I can't open some PDF files - the window opens but the document is blank.

Hi there!

Ive never had any problems opening and viewing pdf files. However I tried to download some from my college's portal (which I have done sucessfully for some months with no problems) and a window comes up but the document is blank??? I asked a friend to go to the portal and try to download these files and it worked for them. Some pdf documents do load but not the ones I really need!

Why would it suddenly be a problem and what do I need to do - please help!

Mandagk