Have you proved that ioFTPD crashes without any scripts just to rule out wierd dlls being force loaded by 3rd party apps installed on the computer? In particular older versions of netlimiter, etc would randomly crash ioFTPD because they used injected dll that were broken.
Is there a CrashLog file in the ioftpd/system dir along with minidumps? I think ioA/B has a login event, does removing that fix things until you try to do something that uses either script?
You gotta provide more info