In order to avoid an ugly bug in Netbeans 6.5, one which removed all rake functionality from the Netbeans IDE, I installed the latest build of Netbeans for Ruby (and RoR). Unfortunately, this install messed with my Mercurial settings and it took me around half an hour to track down the issue.
Tools->Options->Misc tab->Versioning tab->Mercurial
The Mercurial executable path wasn't imported correctly, Netbeans was unable to find hg.exe.
Its nice to have rake tasks...