I switched computers so I redownloaded Desktop Manager (first 4.5 then 4.7) but neither could connect my BB. Windows loads the driver and in my taskbar my bb shows up and even the question if i want to use my BB as mass storage pops up but DM can't lock onto my usb connected BB 8330.
What I had to do is, make sure that everything Blackberry is removed from your computer. Control Panel>Remove Programs, etc. That may not remove everything though. Go into Windows Explorer and check there as well. Look in both programs and common files. I found an old version by looking in Explorer and after removing that I reinstalled 4.5 and all is good. 4.7 apparently is still causing problems.
Hope this helps.