I hate it when a script gets too long Scratch crashes. The weird thing is, sometimes I've had longer scripts that didn't crash. This is 0s1s, another crasher was 47 sprites and 155 scripts.
Offline
It's the length of the script that's the problem, not the number of them. Squeak actually draws the script on the scripting pane, so whenever you move a script, it has to redraw the entire thing. Naturally, when a script gets too long, it takes a long time to draw. I've never heard of a crash though. Maybe a memory error?
Offline
It freezes up with a long script.
Offline
Make a script in pieces, then put the pieces together in descending order and you shouldn't have a problem.

Offline