That line is only added conditionally to new projects, its not added for example when targetting processor expert.
I think the original post does not contain enough information to diagose the issue yet.
I wounder therefore
- which version? (IDE 5.9 is the editor version...)
- which target connection?
- a log of the download?
- when disabling verify, how does the memory at 0xFF80 look like? What is different
- are the remaining parts of the app properly flashed?
As wild guess: the Serial monitor does vector redirection, so with the serial monitor something written to 0xFF80 ends up at the redirected vector location.
The probable best way to check this is to enable logging in the target connection.
Daniel