I have just updated to 4.5 (4.50.0.1843) and am running on a MBA (2011), 13", 256SSD, i5, on Lion.
I have a shortcut for the ESV in the ribbon as per screenshot below,

On the stable 4.3 version, I was able to drag the ESV shortcut in order to open in a panel with the three-fingered gesture on the track pad or with a click and drag. This action now causes RC1 to go insane and ESVs replicate at an uncontrollable rate wherever the trackpad pointer happens to be resting.
The only way to prevent the replication is to force quit. When opening up L4 to the layout in use before the error, L4 functions as expected... Until one tries to drag the ESV from the ribbon.
This activity is repeatable.
I enabled diagnostic logging and then replicated the drag and drop action. I have attached the logs, hoping they might be of use.
8156.Logos4.log.zip
Strangely, other resources are not effected. The NA27, for example, can be dragged from the ribbon without incident.
Andy
Edit: I have tried deleting the ESV and then re-adding the ESV to the ribbon. The behaviour still repeats, but the replication now ends after four or five unneeded ESVs have opened seemingly by themselves.