I posted a thread about this problem, and I am still suffering from it (thread title was something like : projectmanager looks weird).
Sometimes it happened, sometimes not. Very strange.
I did not find a a good way of reproduction yet. When you don't expect it, it happens, and when you want to see it again, it is suddenly gone.
Might indeed have something to do with default.conf, or with CRC (layout crc is another such problem : debug bar gone, ...)
Lieven