draw_rgb_32_image sigsegv

[<james jwm-art net>]

Hello,

My program has a drawable to display gfx, using a custom event_expose
callback to redraw the gfx as needed via draw_rgb_32_image. It works
perfectly fine until I increase the image size by a factor greater than
1.73.  No matter which size image the program starts with, if it's size
is increased by a factor greater than 1.73, it seg faults, (or if it's
reduced to less than 80 px).

gdb backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x406a3ba0 in gdk_rgb_find_color () from /usr/lib/libgdk-x11-2.0.so.0
(gdb) backtrace
#0  0x406a3ba0 in gdk_rgb_find_color () from /usr/lib/libgdk-x11-2.0.so.0
#1  0x406a3c0f in gdk_rgb_find_color () from /usr/lib/libgdk-x11-2.0.so.0
#2  0x406a4801 in gdk_rgb_find_color () from /usr/lib/libgdk-x11-2.0.so.0
#3  0x406a4b36 in gdk_draw_rgb_32_image () from
/usr/lib/libgdk-x11-2.0.so.0
#4  0x402cef14 in Gdk::Drawable::draw_rgb_32_image () from
/usr/lib/libgdkmm-2.4.so.1
#5  0x08060184 in viewport::on_expose_event (this=0x80abfa8,
event=0xbffff660) at viewport.cc:113

..snipped to #26

I've checked and rechecked my code, that I have converted it correctly
from the C/GTK-2 version, and cannot see any problems.

If anyone can make any suggestions (from similiar experience) as to what
perhaps I may have missed I'd be gratefull, otherwise I could make the
source code available if anyone is that bored with nothing to do ;)

ta,
James.