why cant i view pictures in pdf files ?

I think you may need to get Adobe Reader in order to read some PDFs. I had a similar problem a while back because some professors would post readings in that format, and Preview can't read them correctly.

I assume your computer is otherwise updated?

Hmmm... does this only happen in one browser? Have you tried using a different browser for those PDFs that don't work?

Odd, that .pdf displays just fine for me. Though I viewed it by downloading it in Firefox and viewing in Preview.

Have you tried that, or are you viewing your files through Safari?

Could possibly be a Safari issue.