What if you try to load the visor module yourself before attaching and starting the hotsync? Also, is it possible that your hotsync cable is the problem? My Treo 650's hotsync cable started getting more and more flakey as I used it, eventually I bought a BlueTooth adaptor to get away from having to use the usb cable anymore. I always had to remove it and plug it in firmly then not touch the Treo or cable, then it would usually work. Otherwise, sound like something changed in FC4. Hopefully it won't mess with me syncing over BlueTooth, I haven't updated yet. :o Good luck.
