If you still have a problem after consulting this section, then you may have found a bug -- please report it! See Section See section How to report a bug in the GHC system for a list of things we'd like to know about your bug. If in doubt, send a report -- we love mail from irate users :-!
(Section See section Haskell 1.2 vs. Glasgow Haskell 0.26: language non-compliance, which describes Glasgow Haskell's shortcomings vs. the Haskell language definition, may also be of interest.)