I've been running into this issue with cabal 0.10.2, but ONLY in conjunction with GHC 6.12.3.  It's hard to make a small reproducer for (and therefore I haven't filed a bug yet), but you can see the below Jenkins run stalled for 2.5 days, whereas it should take minutes: http://tester-lin.soic.indiana.edu:8080/job/monad-par_github_master/JENKINS_... Note that it *doesn't* burn CPU -- it deadlocks rather than spins. I replaced "cabal test" with a direct call to the test executable and I haven't seen this problem since.    -Ryan