ghc-5.00.2: panic! (the `impossible' happened, GHC version 5.00.2): Oversize heap check detected. Please try compiling with -O.

[Simon Marlow]

> > This is a known bug, but thanks for reporting it anyway.  
> The workaround
> > is as suggested, try compiling with -O.
> 
> I *was* compiling with -O. IIRC the problem occured with any level of
> optimisation I tried if and only if profiling was enabled.
> 
> Any other suggestions?

You could try breaking up the structure into smaller pieces.  If you
have a local GHC build, you can also bump the BLOCK_SIZE to 8k in
ghc/rts/Constants.h.

Cheers,
	Simon