problems downloading PDF files

Hello,

When I try to download pdf files from the internet, the same files sometimes open immediately, sometimes nothing happen, sometimes I'm prompted to save the document, and then when I try to open, sometimes it's opened, sometimes it says the file is corrupt. the files are not corrupt and can be easily opened from other computers.

I think it has something to do with security issues, but I can't figure out how to solve this nuisance.

I have Lenovo R61i, 7732-CTO
Vista home premium

thanks

 

I do, I just downloaded Acrobat 9.

I think it actually has to do with something else, since it also happens - though less frequently - with downloading Word documents