gnumeric crashes when formatting dates to mmmmm or mmmmm-yy

Binary package hint: gnumeric

I'm running Ubuntu 7.04 (hardy heron) and gnumeric version 1.8.2-1ubuntu1.

I can't seem to reproduce this bug from a fresh worksheet, so I have attached one that allows the bug to be reproduced.

Steps to reproduce:

1) open the attached worksheet in gnumeric
2) select all of column A
3) choose format cells... -> Date -> mmmmm or mmmmm-yy

What should happen: The cells are reformatted as specified
What happens: gnumeric crashes with a segmentation fault.

The output from gdb debugger is below.
----------------------
<launched gnumeric and opened file>
----------------------
(gdb) run
Starting program: /usr/bin/gnumeric
[Thread debugging using libthread_db enabled]
[New Thread 0xb6963720 (LWP 10415)]
Reading file:///home/xxxx/buggy_worksheet.gnumeric

** (gnumeric:10415): CRITICAL **: go_date_month_name: assertion `g_date_valid_month (m)' failed

(gnumeric:10415): GLib-CRITICAL **: g_string_append: assertion `val != NULL' failed

** (gnumeric:10415): CRITICAL **: go_date_month_name: assertion `g_date_valid_month (m)' failed
-------------------
<attempted formatting change>
-------------------
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xb6963720 (LWP 10415)]
0xb7bf04ed in ?? () from /usr/lib/libgoffice-0.6.so.6
(gdb) backtrace full
#0 0xb7bf04ed in ?? () from /usr/lib/libgoffice-0.6.so.6
No symbol table info available.
#1 0x00000000 in ?? ()
No symbol table info available.
(gdb) info registers
eax 0x0 0
ecx 0x0 0
edx 0x0 0
ebx 0xb7ca4e88 -1211478392
esp 0xbffed780 0xbffed780
ebp 0xbffed968 0xbffed968
esi 0x8769750 141989712
edi 0x0 0
eip 0xb7bf04ed 0xb7bf04ed
eflags 0x210246 [ PF ZF IF RF ID ]
cs 0x73 115
ss 0x7b 123
ds 0x7b 123
es 0x7b 123
fs 0x0 0
gs 0x33 51

(gdb) thread apply all backtrace

Thread 1 (Thread 0xb6963720 (LWP 10415)):
#0 0xb7bf04ed in ?? () from /usr/lib/libgoffice-0.6.so.6
#1 0x00000000 in ?? ()