WOW I am having the same error, My MAC works fine and I can upload to the UNO R3 all day. So I thought windows 7 was crap I reformat the computer install 2 hours of OS update along with C library and other things. Plugged in my UNO and the same dumb error. No mater how or what order I install these drivers I get the same results. I am going to have to revert back to winXP I think and that sucks because I wanted to not go back in the windows world. If someone ever gets this working I and about 1000 other people will be very happy. All our arduino UNO's are "REAL" :%
Im willing to give access to one of our systems if needed just email me and and you can Teamview in.
This sucks but winXP may be the only option. 