I also have had Entourage apparently freeze on me numerous times. One thing
I discovered in the Calendar was that I had 28,000 - yes, that's right, 28
thousand - items in my calendar. Now, I do get rather busy but that's
ridiculous.
It turns out that most holidays had replicated up to 732 times (732 was the
record for any one holiday. You know how holidays are set up as an all day
event? Well, somehow the same event was listed multiple times on the same
day. It was slowing down Entourage unbelievably, and it would take multiple
seconds to redraw the screen after deleting one. And think of the
synchronising that had to be done...
Ultimately I did a Find for all Calendar events, sorted by Date, then
selected all the multiples and deleted them in a number of massive batches.
That sped things up markedly. I had previously deleted the Exchange
account, rebuilt the database more times than I care to remember, rebuilt
permissions, etc, etc, etc......
Check all your data carefully. Do you really have what you want to have...?