My issue is identical to the one here:
however, I don't seem to be able to find a fix.
I am using Firefox 6 as primary test browser and I can't create any new sidebar, it's always empty!
I filled all the sidebars (left, right, with top, left and right components each) and nothing is showing!
This update really messed up my site! Before most widgets were displayed as a mess but at least I could fix them manually, now I can't get them to show at all.