problem seeing executable file

Dear all, 

I am afraid I have a very simple problem but I am not very good with
Linux. I want to use gdb (here on a test program a.out), but it seems
that gdb cannot see the file even though from the directory it runs
fine. 

bash-2.05b$ a.out
hello world
bash-2.05b$ gdb a.out
GNU gdb Red Hat Linux (6.0post-0.20040223.17rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as
"i386-redhat-linux-gnu"..."/home/jonh/dynamicrewire/numerics/a.out": not
in executable format: File format not recognized

If I type path I get

Executable and object file path:
.:/usr/kerberos/bin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin
 
so the present directory does seem to be in the path.

Sorry for such a stupid question, any help would be appreciated,

thanks,

Jon Hatchett