Welcome to the forums BuzWeaver
I'd recommend you restart your computer first.
Now get on your Droid go to settings, look for the SD card section, unmount the disk and then click on format. After thats done take a picture, if you can't powercycle the phone and try again.
After you take the pic connect the Droid to the computer tell the Droid to mount the SD for the USB function.
If that doesn't work pull the battery and reinstall the the SD card and do the steps over again from unmounting to formating to taking a pic etc.
This should work