Fitting Internal Error caused by SignalTap nodes

Try turning off incremental compilation. You won't get the incremental compilation compile time benefit for recompiles after changing SignalTap settings, but turning off incremental compilation might at least get around the internal error.

With a later version of Quartus you will probably at least get a normal error message instead of an internal error. I don't expect a newer version to prevent the error entirely, but it might if your situation is different from the one I know about. In any case, a newer version of Quartus might have other benefits for you. You can install a second copy of Quartus (a second copy of the QII 7.2 base version onto which you can add a 7.2 service pack or a regular QII 8.0 install) so that you don't lose access to your QII 7.2 with no service pack.