@ The Dodo:
We run version 5 SP4 at the moment, but are planning to upgrade to V6 SP2 whitin a few weeks. We use full text indexing, so processor utilisation is always high; that's not really a problem, we are used to that. The application crashing because it run's out of memory was a problem though.
Unsetting the 4GB switch seems to do the trick.
Thanks all for the responses!