jpg corrupt on frontpage publish

Big HELP. I have been happily publishing my site for a while using frontpage 2002. for the last 2 weeks the pictures on my sites are corrupted when viewed from the site. click on any thumbnail on URL . if i copy the files back they are now corrupt although appear to be same size etc.

i have published to a different site URL and they are ok.

however the isp for the school site have successfully taken files from the working site and published them to the proper site and they are ok and say they cannot find any propblems their end.
we are in a don't know who's fault situation. Has anyone come across this before or can anyone suggest questions i should be asking of the isp

The pictures look fine to me? What corruption should I see?

the thumbnails are fine but the actual pictures mainly consist of lines e.g.
URL
- have also (hopefully) attached one that i copied back of the site which should appear corrupted.

How weird, I've never seen anything like that.

and it gets more interesting - narrowed down to only on http transfers when using broadband! ftp transfers and http on dial up work ok. Am waiting on microsoft - if i get a resolution will post it for future reference.

Just to let everyone know - turns out to be a problem with my Norton firewall - tho' only on http transfers on broadband. Disabled firewall using the norton disable buton but problem still existed. Obviously had not disabled it properly as when i used msconfig i found that if BOTH Norton Internet Security Accounts Manager AND Norton Internet Security Proxy Service are running then the pictures corrupt - if only ONE of them is running then the pictures publish ok.

As i'm on norton 2002 they won't give me free help even tho' there automatic update has obviously messed something up!

Thanks for your help - i just have to decide now if i pay for an upgrade so i can get help!