Found in 0.12.0 on Ubuntu 12.04, 32 bit.
Linux 3.5.0-43-generic #66~precise1-Ubuntu SMP Thu Oct 24 14:55:08 UTC 2013 i686 i686 i386 GNU/Linux
Windows are all white (blank). The outlines of some tooltips and menus show up, but that's it. The various applications appear to be working, they're just not really visible. Went back to 0.11.6 and there was no issue.
Please let me know if I can attach anything useful for debugging.
(Also, not really sure what the component should be. I guessed core.)
Have you tried switching encoding? Does turning off/on opengl help? This could well be encoding related.
Well, that was really obvious when I tried it: the server log file was full of helpful messages.
The 32-bit fix is in r5927, and backport for v0.12.x in r5928. Fix tested on Ubuntu Precise 32-bit full up to date.
I will release 0.12.1 with this fix shortly.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/550