Upgrade to at least service pack 4. The sp 4 fix list has 5 or 6 fixes for memory leaks. I dealt with this battle why back when and this message points to a memory leak or memory pressure in memtoleave. You can also look at bumping up your memtoleave allocation to 386 MG. If you google you'll find lots of references on how do to that.

I'd suggest upgrade all the way to 8.00.2187 if you can.