GD and image resizing

Hi all

I'm using imagecopyresampled to resize images uploaded for a content
management system.

Everything works fine on images up to about 800kb. Anything over and the
file gets uploaded, no errors are created but the image doesn't get
reesized.

I'm assuming from other posts on this issue that it's a memory thing with
the server.

I installed a gallery app that used netpbm that would handle large images
but GD seems to fail.

I've not played with netpbm much but does anyone have any experience of
this? Is it easy enough to manipulate images with netpbm?

Any pointers would be gratefully received.

Andy