Due to a small usability issue on the Mono web site, users were downloading versions that were more than 2 years old!

Only 5% of the Mac downloads were actually getting the latest version, 95% was downloading this two year old version. I don't have my notes handy for Windows, but they were similarly abysmal [Update: found the notes, they were 95% as well].

Read more about how this happened here.

So, if you had a recent experience with Mono -- you might want to check to see if the version was current!

(Mono is an open source implementation of .NET for client and server applications).