one problem I noticed on our exchange environment was every time I did a manual sync it created a new device partnership on the exchange server. At the time I was running 1.0.1 rooted though. I haven't tried 1.1 yet. If you have access to your exchange infrastructure you may want to check out how many device profiles you have associated with your account. Exchange I think has a set limit of 10 partnerships per user.
On a similar note touchdown doesn't seem to want to sync on froyo either. however I think it's having trouble getting past the 2010 device policies. Strange that it works on my hero.