I'm away from my desk at the moment, so I can't help a lot, the only official ultraVNC thread I found about this issue is here:
http://forum.ultravnc.info/viewtopic.ph ... 62ce71ad39I'll see what I can do to help as soon as I can (hopefully tomorrow night). In the mean time, you should be able to install using the provided exe (from here or cnet). If you are prompted to download extra stuff (mirror drivers, etc), you can safely not do that for now (they are not REQUIRED). Once the problem is straightened out, you can go ahead and reinstall if you need the extra performance.
Thanks,
Raf.