I do not have OL2003 to test with, but will share a recent runin with a firewall that was pegging the CPU meter and such tasks would not run.
Check to see what tasks are running and see if the CPU seems to have idle time.
I've been using the Outlook personal folders backup utility for quite some time, but in the past few days it has been acting strangely: When I try to make a backup, nothing happens until I shut down Windows, at which point the "making backup" box appears on the screen and seems to create the backup (I've no idea whether it's actually able to finish; it seems like Windows shuts down too fast for that). Prior to these past few days, it has been fine.
Any ideas? Thanks ahead of time.