can upload gif but not jpg

I am running phpnuke 5.6 on a linux box running latest software. I have installed gallery 1.3 and it works fine when i upload a gif picture, makes a thumbnail fine, but when i upload a jpg i get this errer. WHY!!!

Processing status...
- Adding 8310e.jpg
Executing:

/home/lukey2/public_html/netbpm/jpegtopnm /home/lukey2/public_html/albums/album03/8310e.jpg | /home/lukey2/public_html/netbpm/pnmfile --allimages

Results:
stdin: Image 0:

Error messages:
pnmfile: EOF / read error reading magic number

Status: 1 (expected 0)
Error: Invalid image: 8310e.jpg!

if sombody could explain what this error is, I would be very gratefull.

Regards

:grin: