HTC Sync not working with Outlook 2010 x64 =[
No doubt because of 32/64-bit MAPI incompatibilities. Basically MS are providing no interoperability or "thunking" layer for this so no 32-bit MAPI client can talk to a 64-bit MAPI server, such as Outlook x64. Until HTC write a 64-bit version of HTC Sync, I suspect you'll be stuck.