Can you give us the line number of a few of the errors, and the relevant portions of the header file around those lines?
Also, if you can right-click a source file and then select Preprocess, that might give another clue -- there will be #line directives you can search for to get yourself to the relevant portions of the preprocessed code.
The preprocessed header will start with a line like:
/* #line 1 "MCF51JM128.h" */ /* stack depth 2 */
Of course, you also want to be sure there is nothing in your files *before* any of your #includes that could be causing problems... That can also confuse the precompiled headers operation as well.
I assume you've tried removing all object code, and even removing your <project>_Data directory?
-- Rich