Unfortunately I can't give a quick answer ... I'm not aware of any new problems quite like that ... Any version of 1.4.x after 1.4 is only getting more stable, not less. I'm going to release 1.4.1 today, in fact, to get some of the recent (minor) fixes out there.
As it turned out the Wiki "problem" I mentioned was not actually a problem in the Wiki module at all, but a glitch in my PHP accelerator. Perhaps you are having some server problems too?