Some of my users complain that they have to reload page to see their new posts and topics after they have posted them. I have also notices this when working in public internet cafes. "no-cache" does not help.

It could happen when you are using proxy, and it would be a proxy problem.

Any ways to solve it?

If proxy stores copy of the page on its server, there is no way to solve it, if only to fix the proxy.

Anyway, admins are often concentrating on user problems too much... If you are admin of forums, we recommend you simply to forget about this users problem - it doesn't affect forum script in any way. You are not responsible for users problems, even if they are saying so.