This was happening in 5.0 (most recent SR), but I figured out the underlying issue just now, immediately after installing 5.1.
I have a layout which includes a note file. For unknown reasons, when the L5 starts and this layout opens automatically (which is desirable), that note file has the focus (something I'm sure was not the case when I closed Logos). The text carat (cursor) is in the "content" field for one of the notes in the file. If I hit Ctrl-L in that situation, nothing happens. If I click on some other resource tab (e.g. my preferred bible) and then press Ctrl-L, the library comes up as expected (well - not as expected - it doesn't retain the size or sort order from the last time it was up; that's a long-standing bug 
.
I can repeat the behavior by giving control back to that (or any) "content" field, or even the field for the note name/text.
Thanks for delivering 5.1 !
Donnie
