I am not sure where the problem is either.
Maybe it has something to do with setting the interrupt registers before the instants are enabled. Darrel.s routine sets these so you do not need to do it.

Reading through other post this seems similar (post 52 and 53). I am sure you have read them but it is all I can find at the moment.
http://www.picbasic.co.uk/forum/show...3402#post23402

And I think this is related
http://www.picbasic.co.uk/forum/show...=9786#post9786

Did you say what PIC you are using?