After installing version 1.2A in its own directory, but sharing a proflile with version 1.1 both versions began having the problem of the bookmark list not scrolling down. It will scroll up even if the mouse is not on the arrow, but going down only one line at a time if the mouse is moved on and off of the arrow. I got 1.1 to work correctly by deleting 1.2A and the whole profile directory and then restoring the profile directory copy that I had saved before installation. BTW, I am using environment variables for Mozilla_Home and the Profiles directory.
Sharing a profile between two different Mozilla versions is an invalid scenario.
or dup of bug 163104