office XP

Hi all

We have exchange server 5.5 with sp4. We have 2 problems with XP outlook.

1. Reply button take several time for it to work
if I do for the first time it return back with error message
2. I have a remote user who has to manually click on send/recieve to recieve email from pop account.

Everything is working fine on office 2000. I could just reinstall with office 2000 but I like to find out why is it happen with xp?