internal error: awaitEvent: descriptor out of range

My program reports:

Server3s.exe: internal error: awaitEvent: descriptor out of range
    (GHC version 6.8.2 for x86_64_unknown_freebsd)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Abort trap: 6 (core dumped)

The core dump shows:

(gdb) where
#0  0x0000000800956dec in kill () from /lib/libc.so.7
#1  0x0000000800955c5b in abort () from /lib/libc.so.7
#2  0x00000000004e5bcd in rtsFatalInternalErrorFn ()
#3  0x00000000004e58bc in barf ()
#4  0x00000000004ea57d in awaitEvent ()
#5  0x00000000004e6d85 in scheduleWaitThread ()
#6  0x00000000004e42a9 in real_main ()
#7  0x00000000004e4398 in main ()

My host is:

FreeBSD hpsux 7.0-RELEASE FreeBSD 7.0-RELEASE #0: Sat Mar  8 14:07:11 HST 2008     root@hpsux:/usr/obj/usr/src/sys/GENERIC  amd64

The full sources that are causing this issue are attached. To reproduce: run "make" then in one window run "./Server3s.exe" and in another window run "./DummyClient3s.exe". I get the crash in the Server3s program after it runs for a while.

I can provide built binaries and a core dump if it is helpful. I didn't include them yet because they are large.