Hmmm. Segfaults are really difficult to track down - I can't reproduce this problem on my Linux machine. Here's what I get:
Prelude> ord 'a' [Compiling... ==================================== Error when renaming:: Identifier ord used at 10:21 is not defined. (in overlap resolution) ...failed] Prelude>
I'm pleased to report that rebuilding (using the nhc98 I had previously built with gcc) created a working executable. You might need to modify the build rules such that hi does not function unless built with a true Haskell compiler. This is probably due to some kind of interaction between the version of gcc, libc, etc., on the system. I'll verify on Linux, but I suspect the result will be the same.
And this highlights a side issue - you should note that Hugs is naughty to accept the expression at all - ord is not in the Prelude. For true Haskell'98 behaviour, you should :load Char first.
Prelude> :load Char [Std module... /usr/local/include/nhc98/Prelude.hi] [Std module... /usr/local/include/nhc98/Char.hi] Char> ord 'a' 97 Char>
And this works as well.
But of course this doesn't help you. You said that you get the segfault under both Cygwin and Linux right? That suggests a fault in the code, rather than an environment issue. Can you tell me what compiler you used to build nhc98 etc with, under both Cygwin and Linux?
I built both copies using the included 'C' code from the tarball (the gcc target) under gcc 2.95.3 Successful build was achieved by building nhc98 with the C sources, then rebuilding with nhc98 to bootstrap itself. Not sure why this was required, but that works. Thanks, -Brent