For months my phone refused to sync with ANY computer.  I plug it in, it loads the drivers and then nada.  Activesync can't see the phone on any computer.  I'm also using wireless Activesync to sync up my email at work through Exchange 2003.  I googled around and couldn't find a definative fix so I followed them all.  Upgrades, downgrades, hacks and even dancing around singing Joy To The World while rubbing my belly.  Nada!

I did stumble across someone saying something about having more than 100 contacts in Outlook.  Well, I had my phone plugged in and Activesync sat there with it's defiant grey "not connected" symbol laughing at me.  I started to delete old contacts and merging some (do I really need 5 separate contacts for one person??) and after a few the Activesync turned to a happy green and started it's hypnotic spin.  Viola!  

So the fix is keep your contacts under 100.  Since I'm at 99, I'm not allowed to meet anyone ever again - I think I'll be OK with that.