This is a common problem. See http://community.logos.com/forums/p/30476/225712.aspx#225712 which includes wiki instructions etc. The key is to save at the bottom and then at the top (twice). Kind of not so obvious.

hmm ... when i click on save it brings to a page that says:

Are you lost?

That is a new evangelistic outreach program. [:D]

Even when you save it per the instructions, it still takes a "while" to show up. I like to think it is the forum nanny approving all pics uploaded but I think it has something more to do with the Logos servers using mirrors for updates & maintenance procedures.  Don't worry, if you can see your new avatar on your own profile page it will eventually show up. Unless you have incurred the wrath of the forum nanny! [:@]

I think there is actually a bug in the forum software. I've gotten this 404 error page as well, with the clever "Are you lost?" sheep thing. I've been meaning to report it to the forum developer but had forgotten about it. I will direct him to this thread.

Documenting the frustrating experience of trying to change your Avatar, for the benefit of Logos forms developer(s) whom I will refer to this thread:

(1) Click the "Edit" button at upper right of any forum page, near your name that you're logged in as:

(2) This takes you to the Edit Your Profile page, where you can click Change Avatar:

(3) This takes you to your Logos.com profile (a bit confusing but OK) which has your avatar stuff in the upper right corner:

Confusing bit #2: It says "Choose a picture" and "No file selected" but the "Choose File" button is greyed out, so one is puzzled for a while as to how to actually choose a picture. Ah, but soon you discover that...

(4) If you hover over the existing picture, you'll see a Delete button show up. Click it.

(5) This deletes your avatar, and you see this:

But you think "Wait a minute!" The "Choose File" button is still greyed out, and I can't select a new avatar. I don't want to keep this change! I'll keep my old avatar at least. No such luck.

(6) Try clicking Cancel (which ironically you can do, even though it's grey, which seems like a bug to me, or at least it's confusion #3 or 4 -- I'm losing count) and you get this:

Cute sheep, but no I'm not lost. I was just trying to cancel the change of my avatar.

(7) Click "Account" in upper right to get back to your main Account page:

(8) Oops, it appears that the avatar was changed after all; the operation was not (apparently) cancelled:

That is actually not the case (which is incredibly non-intuitive; confusion #4 or so), as you can only tell if you go to some page on the forum where you've posted before and refresh it and see what your avatar looks like there:

(9) So now get back to your Logos.com profile page. This time get cheeky and try clicking on the greyed out "Choose File" button anyway, in spite of the fact that the mouse does not change to a hand pointer as it does over the greyed out "Cancel" button. It actually changes to an insertion point icon of all things:

(10) Clicking this allows you to select an avatar image file from your hard disk, and that causes the Upload button to appear and be enabled (wow, so far the first thing that actually makes logical sense):

(11) Click "Upload"; oops! you forgot this was a 5+ megabyte file, and you end up with this error message:

(12) Click the Back button on your browser to try again. Click "Choose File" and select a different picture. Click "Upload" again. Nothing happens. No error message, but no sign that any uploading is going on whatsoever. BUG! There seems to be nothing you can do to select an appropriately sized file and try again. In exasperation, click Cancel and get the sheepish 404 error message again.

(13) Come back to your profile page afresh again via your main Logos.com account page. Try it again, and this time select an appropriately sized file, and click Upload. This time it works to upload the new file:

Another confusion, though: the text still says "Choose a picture" and "No file selected." Hmm, never mind.

(14) This time you remember reading something about how you have to click the "Save" button for this operation to take permanent effect, so click it. Aha! Finally (it seems)...success. Hallelujah!

But what's this? You go back to a thread where you've posted before, and refresh the page a couple of times, and still it shows you with no avatar:

(15) Go back to your forum profile page and double check. No avatar [:(]:

(16) Click "Change Avatar" again, and you see the new avatar is there, according to your Logos.com profile page:

What gives?

(17) Click Save again, just for kicks. You get the 404 sheep error message again. BUG!

(18) Navigate back to that thread you posted on. You remember someone saying something about how sometimes you have to wait a few minutes for the change to take effect. It's been LOTS of minutes now, but still no dice:

I'm still unable to get it working. Tried going through all the steps again (skipping the places where I made a clear mistake) and still no avatar. I did get it working once, but I don't remember what I did and cannot get it back again.

If I, an MVP, am having trouble with this, no wonder people are finding it difficult.

Please fix this process!

Documenting the frustrating experience of trying to change your Avatar,

[:O] And that is the streamlined version!  I took several tries and can tell you for sure how I finally succeeded.

If I, an MVP, am having trouble with this, no wonder people are finding it difficult.

You are assuming the MVP star means we know what we are doing. [:D]

The shortened form of this process is that to change the forum avatar you need to change the logos.com account avatar as the forums use the same avatar as logos.com user accounts.

1. From the logos.com/user/edit page (being logged in), click on the Choose File button and select a reasonably sized image from your computer.
2. Click Upload to send the image to our servers. (If there are other profile changes being made, you may want to click the Save button to record those profile changes.)
3. Click the Forums link at the top of the page to get over to the forums.
4. Click the Edit link at the top right of the forums page to edit your forum settings.
5. Click Save at the bottom of the page to refresh your image.

In most cases, that should be all there is to it.

We do need to automate the refreshing of the forum image on the logos.com profile change, but getting time to work on the forums competes with a multitude of other projects.  We could probably do better with the some of the obviousness of the image upload on logos.com profile (gray for a file chooser button when we normally use gray for cancel or disabled buttons? really?)  but it should be usable at least. I didn't get the 404 sheep appearing in any of my testing, but I may have taken slightly different routes than you did. 

Well I see it did finally work - the forum nanny must have logged on sometime today and stamped her approval