Not a common problem. Sorry.
The next thing to try is resetting Mathematica's front-end initialization files, in case one was damaged. This can be done by holding down the SHIFT and CONTROL keys as Mathematica starts.
If that does not correct the problem, please send the output from running
The whole notebook with the input and multi-tab output can be attached to email to
Does the Documentation Center (under the Help menu) work ok? It can be sensitive to Java problems.