Upgrading to HTC Sync Version 3.2.20 for Android Phones fixed my connection problems
Ever since I got my HTC Merge (Android) from Verizon, I have been using HTC Sync to sync my Desktop Outlook Contacts and Calendar and it worked great - when the connection worked. Connecting my phone with a USB cable didn't always launch HTC Sync on my PC. Rebooting my phone and/or rebooting my PC sometimes helped, but the problem continued.
In May 2012, HTC released Version 3.2.20 of HTC Sync. The change log lists Updated USB driver to 3.0.0.021 and Enhanced connection stability among the improvements. I'm not sure which of these fixed the problem, but I've had consistent success connecting and syncing on the first try. If you haven't upgraded yet, I highly recommend it.