This has happened twice now, not sure what triggers it though. Suddenly all of the buttons disappear, and tab switch from edit to obj mode stops working- I can still select things in the 3D viewport though, and also the pulldown arrows work but display nothing. Using official 2.62, ubuntu 10.10 64 bit, nvidia 9600GT with driver 270.41.06 It's happened on 2 seemingly different occasions, once while adjusting a mesh with an array modifier, and another while changing the sunlight settings, or between renderings (f12).
I put about 6-8 hours in with a build from fish on graphicall, 45447 with no UI issues (he builds on 10.10). I will have to do some testing with a recent buildbot build to see if it's been fixed.
I've heard about this issue before, but haven't been able to reproduce. If you're running this from a terminal it will probably show a useful python error to investigate this, without that or some steps to redo the problem, there's not much we can do here.
The 2.62 build was straight from the blender.org site, no custom settings at all (yeah I'm that hardcore :P). Also, logged in about 5 more hours with the fish build, no issues. If I proceed with testing official builds, would it be better to keep using 2.62 or a build from the buildbot? Thanks for the great tool Blender team!
Which build you use for testing this doesn't matter all that much, it doesn't seem like an issue that would be related to a specific build. I've had it reported some months ago on a Mac, but there was also no way to redo it. It might have been fixed accidentally as part of another problem but it seems random enough we can't tell.
The same thing happened to me as well. At first i noticed it in combination with luxblend when the render was aborted. But it happend to me in cycles as well and also if a render was aborted, either inside the rendered preview or a normal render. Must be some kind of synchronization problem if the render-thread dies.
I think in the near future I will test this in the -d mode, in the official build. It happened twice in two sessions in the official build, while not in the fish build (which has some extra patches included, so it's weird that it was more stable). I assume everyone experiencing this is using Linux 64 bit?
Unfortunately this issue shows up his ugly head more than ever again with b2.64a and later.
With external renderer it get really annoying sometimes, although the crashes are ramdom.
Experiences go far alo for lux-users: http://www.luxrender.net/forum/viewtopic.php?f=16&t=9118&sid=f33dafc02613f2a84ad914ea75948259#p87013
We should really get rid of this, nowadys i have phases where this takes all the fun away by collapsing every few minutes.
Fix in svn, by restricting context access from threads so they can't influence UI context. Both this example script and luxrender still work fine without any changes needed in my tests.