When trying to hook up my BB Curve 8310 to my computer it doesn't get recognized. The charging icon comes on the screen for about 3 seconds and disappears. Yet when I plug it into an outlet with a my charger it work fine and charges fine. For some reason only connecting to my computer it doesn't work. I was going to update my OS 4.5 because AT&T finally released the official version.
The DM install includes the USB drivers for your BB. Once it's installed, you don't have to run DM to connect. Also, I think there is a separate USB drive that can be installed without DM.
Try rebooting your computer, since you just updated DM it might help.
What did you update your DM to? If it's DM v4.7 that is a buggy version. Use Add/Remove programs to uninstall v4.7 and reinstall v4.6, then everything will be good (probably).