HTC Sync without fail is a piece of monkey feces wrapped in elephant dung. I've never gotten it to work.
On the other hand, I just downloaded Droid Explorer which works so freaking well I cannot believe how amazing it is. Initially, i could conect my device, but couldn't see the directories, etc. Turned out busybox was read only and wasn't allowing me to access it on the device.
There are a few caveats:
have to be rooted (fully rooted)
May have to install busybox (I got help from the developer and you can see my post about how well it worked once I followed instructions on how to install busybox). They're part of the discussion I posted (link below) that was questioning if the Evo was compatible with Droid Explorer, after busybox installation, it is. WIthout fail, I am able to do so much that HTC Sync cannot do. A few parts of Droid Explorer are still under construction, but the application is great.:
http://de.codeplex.com/Thread/View.aspx?ThreadId=221342