> Now the question is, if the same problem occurs, why?  Please paste
> the contents of /etc/fstab and, if it exists, /etc/fstab.d/$USER
> into your reply.

Thanks for the information, I think we're getting closer to finding the problem.

/etc/fstab doesn't have anything in it apart from comments, and the
/etc/fstab.d directory is empty.

Here is the output from the mount command:
C:/cygwin/bin on /usr/bin type ntfs (binary,auto)
C:/cygwin/lib on /usr/lib type ntfs (binary,auto)
C:/cygwin on / type ntfs (binary,auto)
C: on /cygdrive/c type ntfs (binary,posix=0,user,noumount,auto)
E: on /cygdrive/e type ntfs (binary,posix=0,user,noumount,auto)
Segmentation fault (core dumped)

It fails when it reaches a network share.  Looking at them in Windows
Explorer, they're all NcFsd network shares and this is a Novell client
machine, if that's any help.

There is some interesting output from a listing of cygdrive.  I'm not
sure why the owner/group is different for the network shares or why
the dates are 1970.  I can also list files in the network shares, so
they're definitely mounted.
$ ls /cygdrive/ -l
total 16
d---------+ 1 TrustedInstaller TrustedInstaller 0 Aug 13 16:19 c
drwx------+ 1 SYSTEM           SYSTEM           0 Aug 13 16:19 e
drwxr-xr-x  1 keleigh          None             0 Jan  1  1970 h
drwxr-xr-x  1 keleigh          None             0 Jan  1  1970 i
drwxr-xr-x  1 keleigh          None             0 Jan  1  1970 j
drwxr-xr-x  1 keleigh          None             0 Jan  1  1970 k
drwxr-xr-x  1 keleigh          None             0 Jan  1  1970 z

I compiled your test C program (gcc -Wall -g mount_test.c -o
mount_test) and ran it under gdb, logging the output to a file
(attached).  It also fails when it gets to the network shares.  I
tried disconnecting the shares and rerunning this program and
XWin.exe, and both worked normally.

I have cygwin_debuginfo installed, but didn't get any useful debugging
info from gdb.  I also tried the same tests on the latest Cygwin
snapshot, but the results were identical.

Any thoughts on why the network shares are causing this behaviour, or
is this a red herring?

Cheers,
Chris