Ideas:
Could be an issue with an under powered USB port... Use the cradle and the external power supply...
Make sure no other programs are competing for use of the USB port by disabling them (such as HotSync for the PalmOS)
Let your Outlook finish syncing before you attempt a file transfer...
Make sure your USB Port driver for your PC are up to date... You might even need to switch out the Vendor suppied drivers for the Microsoft versions, or visa versa...
Try WM5torage... Its a great program and faster than ActiveStink...
Try a different PC and/or OS... You might try creating a VMWare XP Virtual PC and connecting to it from there... (This is a good way to Flash a ROM too if you can't get Vista working!)
Good Luck...