Are your other applications also acting up? If so, you might have a problem
with the hard drive upon which Entourage is installed.
But before you check that...
As a matter of good practice, if it's been a long time since you last
defragmented your hard drive, you might consider doing so. Doing this puts
all the files on your drive in continuous blocks -- as opposed to having
bits and pieces of files all over the hard drive.
It's generally not a risky operation unless you have very little free space
(and in which case it takes forever). However, to be safe, backup your
important stuff (Documents folder, music, etc.) to another volume or to
CD-ROM/DVD.
Then, boot from a startup CD (usually Install Disk 1 that came with your
Mac) so that the hard drive upon which OS X is installed is NOT running the
machine. Then open up Disk Utility and defragment the volume. It can take
anywhere from 30 minutes to an hour or more depending upon how full your
drive is.
When that's done, reboot the machine normally and test Entourage. If it's
still a problem, then I suggest launching the Hardware Test program and
allowing it to run a full test on your machine -- all hardware will be
tested, and it will inform you if it finds problems (and usually fixes
them).
Hope this helps.
Craig
San Diego, CA