Mach3 without the licence will allow up to 500 lines of code, but the line you've quoted is line 152 in your file, so it doesn't look like that's the problem. Just to be sure though, in mach3 goto 'help' then 'about' and see what it says under 'Licenced to'. I don't think there's anything wrong with that particular line, since for instance it's identical to line 15 (N65).

It wont help with the current problem, but either way try putting G64 at the beginning of the code. This will make the machine run in 'constant velocity' mode, instead of 'exact stop' (G61) which causes it to move exactly through each co-ordinate which often makes the motion not very smooth.