A run-time error message box means something has gone wrong in Quest. It may be that a mistake was made in your ASL file, but when that happens Quest should be checking for it and printing a message telling you what's wrong. So, whether there's a problem in your ASL file or not, there is something wrong with Quest.
If you could send me your ASL file (email me at
[email protected]) and tell me which version you're using, I'll take a look into it for you.