> A colleague is having trouble with code that runs fine on the 18C but
> not on the 18F.

Well, we found the problem.  It wasn't a gotcha, it was a duh.
The project was set up to be able to quickly change from the 18C to the
18F part - pretty typical.  One of the items unique to the 18F compile
is an initialization of the built-in data eeprom.   That code had been
lifted from an earlier 16F876 project.  The logical address for eeprom
data on the F876 is 0x2100, which just happens to fall smack in the
middle of the 18F452's program space.  So whenever the project was
switched over to the flash part, it was being commanded to over-write
part of it's program.  Just another case of computers doing exactly what
they are told to do.
If anyone is interested, the logical address for eeprom data for the
18F452 is 0xF00000 (five zeroes), and it seems to write in words
instead of bytes.

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