You need to install the software from a separate installer CD, you cant just run the setup file on disk 1 of the City Navigator CD's, it doesn't work.
I bought a used BMW Nav 2 (same as 2610) and phoned Garmin, who registered the unit in my name, sent me City Nav V6 CD's plus the install code by email but they forgot the installer CD. I had to get a copy of the installer CD from my local BMW dealer to install it as the second time I phoned Garmin I spoke to a different guy who wasn't willing to help me.
Try ringing Garmin UK on 0870 850 1242 then press option 2. You will be put in a queue, ask to speak to Mark Timms, he is the helpful one there and a top bloke, I dare say he would send you an install CD.
You can download the map update to V6.5 from the BMW Motorrad website by searching through their navigation systems page and clicking on downloads. I expect this will work on the 2610 as it uses the same mapping software as the Nav 2 unit. Its worth a try.
Good luck.