If you can post your site URL, it will help us to locate the possible problem.
I am really sorry, without a link to a page that has problems, I am unable to locate the source of the problem. Maybe, someone else will come up with a solution.
- In the meanwhile, you can try deactivating all plugins and see if it helps.
- Switching to Twenty Eleven theme so that you can know if the problem is theme-specific.
- Resetting permalinks that sometimes can help.