Hello, $ cabal install category-extras Resolving dependencies... cabal: dependencies conflict: ghc-6.10.1 requires process ==1.0.1.1 however process-1.0.1.1 was excluded because ghc-6.10.1 requires process ==1.0.1.0 What does this message mean? It makes little sense to me -- ghc-6.10.1 requires both process ==1.0.1.1 and process ==1.0.1.0? And, more importantly, how do I solve this? Below is my output of ghc-pkg list. Thanks much, Martijn. $ ghc-pkg list /Library/Frameworks/GHC.framework/Versions/610/usr/lib/ghc-6.10.1/./package.conf: Cabal-1.6.0.1, HUnit-1.2.0.3, QuickCheck-1.2.0.0, array-0.2.0.0, base-3.0.3.0, base-4.0.0.0, bytestring-0.9.1.4, containers-0.2.0.0, directory-1.0.0.2, (dph-base-0.3), (dph-par-0.3), (dph-prim-interface-0.3), (dph-prim-par-0.3), (dph-prim-seq-0.3), (dph-seq-0.3), editline-0.2.1.0, filepath-1.1.0.1, (ghc-6.10.1), ghc-prim-0.1.0.0, haddock-2.3.0, haskell-src-1.0.1.3, haskell98-1.0.1.0, hpc-0.5.0.2, html-1.0.1.2, integer-0.1.0.0, mtl-1.1.0.2, network-2.2.0.1, old-locale-1.0.0.1, old-time-1.0.0.1, packedstring-0.1.0.1, parallel-1.1.0.0, parsec-2.1.0.1, pretty-1.0.1.0, process-1.0.1.0, random-1.0.0.1, regex-base-0.72.0.2, regex-compat-0.71.0.1, regex-posix-0.72.0.3, rts-1.0, stm-2.1.1.2, syb-0.1.0.0, template-haskell-2.3.0.0, time-1.1.2.2, unix-2.3.1.0, xhtml-3000.2.0.1 /Users/Martijn/.ghc/i386-darwin-6.10.1/package.conf: HTTP-3001.1.5, binary-0.4.4, brainfuck-0.1, cpphs-1.6, data-accessor-0.1.4, data-accessor-template-0.1.4, extensible-exceptions-0.1.1.0, fgl-5.4.2.2, ghc-paths-0.1.0.5, haddock-2.4.1, haskeline-0.6.0.1, haskell-src-exts-0.3.12, haskell-src-exts-0.4.4, haskell-src-exts-0.4.6, haskell-src-exts-0.4.8, haskell98-1.0.1.0, hscurses-1.3.0.2, iconv-0.4.0.2, lambdabot-utils-4.2, oeis-0.2, parsec-3.0.0, process-1.0.1.1, readline-1.0.1.0, show-0.3.1, smallcheck-0.4, tagsoup-0.6, terminfo-0.3, uniplate-1.2.0.3, unlambda-0.1, utf8-string-0.3.3, zlib-0.5.0.0