You didn't state what computer OS you are trying to use, but sometimes there's nothing you can do except find another computer that works. I used to be able to reliably flash ROMS and sync files to my Behold II with my Windows XP box, then reformatted to put a fresh installation of Windows XP back on, and now can no longer keep a connection to my phone (the phone is recognized, but once I start trying to transfer files/etc, it soon craps out and the event log shows disk controller read/write errors). I used the exact same cable to my Windows XP laptop and it worked fine, so it was clearly a software/driver issue, but removing and reinstalling the drivers had no effect.
The problems get even worse if you're running Windows 7 or a 64-bit operating system. Good luck.