My Ocular has suddenly stopped opening pdf files. It however opens dvi files with no difficulty. Does anyone have an idea what is the problem and how do I fix this?
Thanks.

Does it give an error message which may indicate what the problem is? Have you recently updated or installed anything?

No error message! More surprising is the fact that the problem suddenly disappeared, just like the way it appeared: for few days Okular simply refused to load pdf files, and then everything got back to normal....