The newest version of UltraVNC is 1.0.9.6.2, but the version in the crosstie is 1.0.8.2. The crosstie should be updated to use the new executable at:
http://support1.uvnc.com/download/10962/UltraVNC_1.0.9.6.2_Setup.exe
and have the signature updated. Crossties are "community supported," but it's really unclear how to patch or update the crossties. Hopefully, someone will make this happen.
Meanwhile, the installer seems to work fine as an unsupported application, even without the crosstie. It worked for me under Crossover 11.0.0, at any rate.