The ONLY way to move a YaBB install that actually works reliably is do a clean install, test and then bring back the 'data elements'.
As to 'fully supported' - It certainly runs on IIS7. Most of those installs I am aware of are on hosted servers or managed VPS's. That is not a huge number. I would bet all of them are 64 bit installs, as I can't imagine a hosting company installing the 32 bit version due to the memory mapping issue (it would be a non-starter).
Is this an in-house server, a hosted server, a VPS or a VM?
I am aware of one persistent unresolved bug on Server 2008/Active States 64 bit installs. I ran into it myself when I had a running Server2008 in core mode. Basically - you see the same text displayed twice (you'll catch this right away). As a systems engineer, my 'guess' was that it had to do with FastCGI and how YaBB is coded. I have had other reports of the same occurrence.
I don't think you have this problem. So the chances are you just need to set up clean, install, and test.
Make it work, when you bring back the data - the test install is lost, as all the pointers are gone.
The problem here is the low numbers, there's not enough info to say anything definitively.
Did you set up Perl/Application Handler. (like this link)?
http://www.howtogeek.com/50479/how-to-install-perl-on-iis-7-for-windows-server-2...I strongly suggest you don't directly use Windows backup/restore methods for bringing back the data. If the old server is still online, in the same domain and on the same network use a 'copy' method to get the files onto the new server. (could be a portable drive also) When you get to the 'bring the files back' point - copy NOT move the files to their new location, then re-apply all the correct NTFS permissions to the YaBB folders & OK the 'apply to subfolder & files' dialogue. There is (AFAIK) only one file that does not adhere to its parent's inheritance. 'Paths.pl' in the root of Yabb's install folder. It has to be set manually to 'Write' for the IUSR.
Good Luck