I'm running into an issue with the new development server on Windows 7 x64. I've installed the Haskell Platform 2011.2.0.1 run cabal update, and then cabal installed yesod. I then ran yesod init and cabal install. Finally I ran yesod devel on the newly created site. The site came up the first time, but when I went to edit and save a hamlet template the first time and refreshed the page it immediately showed me "System.PosixCompat.Files.setFileTimes: not supported: illegal operation".