Hi--I have an 8320, v4.5.0.81. Desktop manager is v4.6 on Vista. I've had this berry (not my first) for about a week. Intermittently, the dm stops recognizing that it is plugged in. I left it in the cradle overnight, it was fine last night, this morning "disconnected" even though still in the cradle.
Restarting dm doesn't help, restarting phone doesn't help. Restarting Windows restores it to recognizing the phone again.
There have been known issues of DM and Windows Vista not playing nice with eachother.
Make sure your USB cable isn't the problem. If not, I recommend completely un-installing DM and anything that has to do with it from your PC. Then downloading it back from the Blackberry website. HOPEFULLY that might help.
Thanks for the suggestions, I will try another cable first.....didn't even think of that, I am using one of those retractable cables and it wasn't real expensive. If that doesn't work I will try the old time worn Windows solution.....delete all and reinstall.