I've been fighting all day with some WP issue and found an outstanding post about it, I suggest you read it carefully (even though it might be a long read) and remember to never upgrade things just because there's a new version or because someone tells you so...
Early this morning I had a few "Out of Memory" messages in a few of my recently upgraded (to version 2.8.4) wordpress blogs, mainly backend messages, nothing really serious.
WTF?!? Out of memory?
Well, it wasn't that hard to fix it, I just had to change php_value memory_limit to 64M and everything was ok, but then again I didn't feel very comfortable with it and kept searching until I've found this pearl.
READ IT FOR YOUR OWN GOOD (and safety).
Wordpress 2.8 Memory Usage and Bloat, Photo