The following extract is from the user hyphz on Monochrome BBS [telnet mono.org for more info - highly recommmended ;o)] in the file Error Messages <HCOM> But you really can't beat TeX when set on long errors. Getting an error 4 lines long that says something like "While I was evaluating the RHS of this expression, something strange happened, and the left hand side is no longer a variable!".. and then you ask for recovery tips and it says "Proceed, for a laugh."
(From the "Rest" of RHF)