It looks like iTunes 10.5 for Windows breaks HippoRemote’s ability to automatically discover your Windows PC. Specifically, the new version of Bonjour that is installed with iTunes 10.5 only works briefly before failing. Hopefully, Apple will issue a fix soon.
In the meantime, a temporary band-aid is to uninstall the existing version of Bonjour and to install an older version from the link below.
This has restored auto-discovery on my Windows PCs, but I’m guessing it may cause some incompatibilities with iTunes 10.5. I haven’t noticed any, but I’m not a heavy iTunes users. If you run into any issues, leave a comment or send me a support email.