That Darn Mysterious Outlook

I just have an obscure little question I was curious about, if anyone out there actually knows --

Every so often, I get a call from a client who suddenly can't communicate with thier POP server through Outlook (today's call, Outlook 2003). I check settings, all is perfect. Everyone else can pop just fine. Internet access is go. "Can't communicate with server".

Reboot.

Bam, all is well with the world.

So, my question is -- Has anyone ever discovered what exactly is up with Outlook that causes it to just fart out like that every so often with POP accounts and require a reboot?

not real sure but I also use outlook and that use to happen to me alot from the start but I had to go to tools, email accounts, more settings, outgoing server and choose log on and manually enter my user/pass on the user requires authentication part? hope that helps, not sure for them but it fixed mine.