Browser: Safari 4.0.5 on Mac 10.6.3
I didn't have these problems with Safari 4. However, now on Safari 5.0 I am experiencing these logout problems. I also have Mac OS X 10.6.3.
There is no pattern to this. It seems to happen mostly when quickly opening new pages/new windows. There have been reports about this sort of problem on IE/Win, but this wasn't a problem on Safari before (at least on my systems, I run two Macs). I will actually check later with the other Mac, I think I still have Safari 4 on that one.