Hmmm...I'm a little stuck on this one...
Can you schedule the report just as a report - i.e., without the export? Can you schedule it with the export but without the email? In other words, break the scheduling down in to pieces and see if there is a specific option or combination of options you're choosing that's causing the problem.
Also, make sure that the user ID that the CRS services is running under has access to the folder where you're trying to save the exported file.
-Dell