I have a HTC Desire that was on 2.1 and worked perfectly with my works exchange server. But since upgrading to 2.2 I cannot get it to work at all. There are no errors it just synchs forever.
It looks like there is an issue with the Exchange Server certificates and Froyo. I have found a few others with the same issue:
Those links have several workarounds that might solve your problem as long as you can get your IT team to help figure out what is going on.
I have seen several people mention the the Touchdown (appbrain link) app is not having any problems. Touchdown is an alternative to the built-in Exchange sync. It might be the easiest solution for you - though it is a paid app - $19.99 as of right now.
QR Code for the app market: