Ah thank you, changing the metabase file sorted my issue out no problem. Cassini is now operating very well, seemingly outperforming IIS on most of my benchmarks, as well as eliminating a few caching issues I was having with IIS.
For your reference, and in order to re-create the bug, I put "C:/FolderName/" as my path, rather than "C:\FolderName", this caused an argument exception, I am guessing due to the bad string format.
Not a huge problem, but it might be worth providing a way for the control interface to validate the folder name to prevent/warn against this happening again.
Other than this minor inconvenience, testing with UltiDev Cassini is going very well, and I look forward to working with you.