As far as I know there isnt a limited size for a script. It's a text file (.txt, .mrc, .ini but still text) that contains the code. What it might be possible is mIRC not being able to read/understand a very big file, but it's not likely that your channel rules exceed this possible limit. I've seen huge codes in one single file.
What you can do is put the non-working ON Text events in a new file (open notepad, paste them there) and the load that file into mIRC (/load -rs "path\to\file")
Good luck,
Zyzzyx
