A new search routine has been added to be used when "set language fortran" is on. 

The new code fails to fall through to the default searches when the new search lists are empty. Note that this bug was introduced between gdb 6.8 and 6.8-37.

As a result the following fails (notice though that is I reset the language to C it succeeds):

--------
        program array2a
        integer, dimension(3,5) :: arr
        integer i,j

        do i=1,3
           do j=1,5
              arr(i,j) = i*10+j;
           enddo
        enddo
  
        print *, arr
        end
-----------
...
gdb array2a
gdb array2a.exe
GNU gdb Fedora (6.8-37.el5)
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "ia64-redhat-linux-gnu"...
(gdb) set language fortran
(gdb) b array2a
Function "array2a" not defined.
Make breakpoint pending on future shared library load? (y or [n]) n
(gdb) set language c
(gdb) b array2a
Breakpoint 1 at 0x4000000000002b71: file array2a.f, line 5.
(gdb) 

Here is a diff to fix the problem. It just puts the test around the new search rather than returning prematurely. Note that this routine is new to 6.8-39. In 6.8 the language config is simply bound to basic_lookup_symbol_nonlocal.

*** f-lang.c    2010-01-27 11:45:30.000000000 -0500
--- f-lang.c.new        2010-01-27 11:24:46.000000000 -0500
***************
*** 320,351 ****
  {
    struct fortran_using *use;
  
!   if (!block)
!     return NULL;
! 
!   for (use = BLOCK_FORTRAN_USE (block); use; use = use->next)
!     {
!       struct symbol *sym;
!       struct type *type;
!       struct symbol *retval;
! 
!       sym = lookup_symbol_global (use->module_name, NULL, block, MODULE_DOMAIN,
!                                 symtab);
! 
!       /* Module name lookup should not fail with correct debug info.  */
!       if (sym == NULL)
!       continue;
! 
!       type = SYMBOL_TYPE (sym);
!       gdb_assert (TYPE_CODE (type) == TYPE_CODE_MODULE);
!       gdb_assert (TYPE_MODULE_BLOCK (type) != NULL);
! 
!       retval = lookup_block_symbol (TYPE_MODULE_BLOCK (type), name,
!                                   linkage_name, domain);
!       if (retval)
!       return retval;
      }
- 
    return basic_lookup_symbol_nonlocal (name, linkage_name, block, domain,
                                       symtab);
  }
--- 320,349 ----
  {
    struct fortran_using *use;
  
!   if (block) {
!     for (use = BLOCK_FORTRAN_USE (block); use; use = use->next)
!       {
!         struct symbol *sym;
!         struct type *type;
!         struct symbol *retval;
!   
!         sym = lookup_symbol_global (use->module_name, NULL, block, MODULE_DOMAIN,
!                                 symtab);
!   
!         /* Module name lookup should not fail with correct debug info.  */
!         if (sym == NULL)
!       continue;
!   
!         type = SYMBOL_TYPE (sym);
!         gdb_assert (TYPE_CODE (type) == TYPE_CODE_MODULE);
!         gdb_assert (TYPE_MODULE_BLOCK (type) != NULL);
!   
!         retval = lookup_block_symbol (TYPE_MODULE_BLOCK (type), name,
!                                   linkage_name, domain);
!         if (retval)
!       return retval;
!       }
      }
    return basic_lookup_symbol_nonlocal (name, linkage_name, block, domain,
                                       symtab);
  }