McAfee +outlook express/server problems

I just tried to set up a new computer at the office today–and am
currently using a free McAfee trial. Outlook Express refuses to
let me check my email (“send/receive”), and, even worse, the
computer is only online intermittently, kicking me off every few
minutes. What could be the problem? I haven’t installed XP
Service Pack 2 yet.

Thanks,
ssecheck