I can't find a error list in the manual. Where I can find a error list.
The User's Guide 03.2000 has Chapter 7. Error Messages at p165, although I can't see 67 nor "Invalid Expression" in there. However, judging by the error descriptions which are in there, I think it'd probably just say something like, "the expression is not valid" ;-( Perhaps Keil could follow the example of the likes of Microsoft and Borland so that you could just click on an error message and get the expanded explanation?