STORE.EXE process uses 60% of server RAM

My company recently installed a new Compaq ML350 server running Windows 2000 Server, Exchange 2000, SQL 2000, BackupExec 8.0 with Exchange module, and InoculateIT 6.0. All current service packs are applied. We are a small network (20 users) so instead of migrating, I started new with my Exchange and Windows setups. Problem- store.exe process builds in its usage of memory over a 24 hr. period to the point I have to restart it every day because of programs locking up or slowing down due to the infostore mem usage. Normal usage is about 30-40 MB of RAM. It inflates to over 600MB overnight (backup runs during this time). Anyone familiar with this? Pre-service pack problems should not be a factor, I think! I would love for someone wiser than me to offer some good insight.