Help. Large Pictures don't work Advanced Guestbook 2.3.1

I have the max picture size set at 50000kb but when i try to post large pictures and hit submit, the page loads for a while, then opens a blank page. Then the picture doesn't show up when I refresh the guestbook either. The picture I'm trying to load is only 602 KB. Any help?

A pic thats over half a meg is asking a lot. The problem may lie in the thumbnail creation. Do you have thumbnails turned on ?

Yeah, I do have thumbnails turned on with a min. filesize of 12 kb. Does it do better with thumbnails on or off?

The script creates a thumbnail by copying the original image and resizing it. This would proably eat up your servers CPU time with a file that large.