Unfortunately I can't reproduce this without the intel compiler/f90. 
However, the relevant GDB output was:
(gdb) r
Starting program: /home/david/f90demo
[Thread debugging using libthread_db enabled]
[New Thread -151084928 (LWP 24298)]
[Switching to Thread -151084928 (LWP 24298)]

Breakpoint 1, 0x08089e8a in main ()
(gdb) step
Single stepping until exit from function main,
which has no line number information.

sample () at f90demo.f90:72
72      CALL MPI_INIT(ierr)
Current language:  auto; currently fortran
(gdb) watch i
Hardware watchpoint 2: i
(gdb) step
Error in re-setting breakpoint 2:
No symbol "i" in current context.
<bang, seg fault>

This being line when breakpoint.c:949 calls evaluate_expression where
exp is 0.

I propose the attached, which has fixed this seg fault on my system. 
Permission to commit?

2004-10-17    <dsl@sources.redhat.com>

	* breakpoint.c (insert_bp_location): Regenerate expression in
	breakpoint owner for watchpoints if null.