CFFile Upload fails over VPN?

hi all,

One of my developers has created a simple file upload routine that works fine for me when connected directly into out network, but when he uploads a file it seems to upload fine but if an image, it's corrupt and text files come through blank (although showing the correct filesize).  After a few hours of beating our heads on the desk the only thing we could come up with was that he is connecting into our network via VPN.

So, just wondering if this is a known issue or just something very odd going on and if it is relating to the VPN access, is there a solution?

Thanks