Since I'm hopelessly stuck with an weird infinite loop (that consumes 0% CPU time!), and since I can't find the problem using "trace", I wanted to try GHC 6.7, which seems to container a debugger (woohoo!!!). Currently I'm using GHC-6.6.1 on Windows. So I grabbed ghc-6.7.20070824 (=the latest one for Windows I could find) and the "extra-libs", compiled and installed the GLUT package (which I needed), but when I compile my library, I get Could not find module `Data.Map': it is a member of package containers-0.1, which is hidden So I tried to expose it using GHC-PKG expose containers-0.1 which worked find, because GHC-PKG list prints d:/app/ghc/ghc-6.7.20070824\package.conf: Cabal-1.1.7, GLUT-2.1.1, HUnit-1.1.1, OpenGL-2.2.1, QuickCheck-1.0.1, Win32-2.1, array-0.1, arrows-0.2.1, base-2.1, bytestring-0.1, cgi-3001.1.5, containers-0.1, directory-1.0, fgl-5.4.1, filepath-1.0, (ghc-6.7.20070824), haskell-src-1.0.1, haskell98-1.0, hpc-0.5, html-1.0.1, mtl-1.0.1, network-2.0.1, old-locale-1.0, old-time-1.0, packedstring-0.1, parallel-1.0, parsec-2.0, pretty-1.0, process-1.0, random-1.0, regex-base-0.72, rts-1.0, stm-2.1, template-haskell-0.1, xhtml-3000.0.2 Anybody has an idea how I can continue? Thanks (again!), Peter