No, I never got as far as configuring the anti-theft module (it prompted me to, but I clicked the "do it later" button).
I'm pretty sure it was Avast - it's the only new thing I've installed since the last (successful) use of HTC Sync. More to the point, HTC Sync started working again once I uninstalled Avast.
Here's what I did:
- Install Avast mobile from Android Market, let it run a virus check. All clear. Yay!
- Plug in USB cable and attempt to use HTC Sync. No luck ("HTC Sync may not be installed on your PC...").
- Notice that USB debugging isn't coming on when I plug in the USB cable. Check settings; USB Debugging has been disabled. I didn't do that, so presumably Avast did. Re-enable it.
- Unplug and reconnect USB cable; try HTC Sync again. Still no USB Debugging, even though it's enabled in the settings.
- Unplug USB, restart phone, reconnect USB, try HTC Sync again. Still no USB Debugging.
- Unplug USB, uninstall Avast, restart phone, reconnect USB. USB Debugging is back on again, and HTC Sync now works fine!