Nope.. you said too much memory, not not enough.
Last time I checked, mySQL liked lots of memory if you would throw it at it and only complained when you were stingy with memory (placing memory constraints on it).
It's more than likely a configuration issue (too much memory, etc)
If you don't have any scripts that are dependent on a lower level of PHP then I would suggest upgrading it at the least.
On mySQL, it's really up to you. I like (personally) to try to keep the latest stable release on my system.