Hello all,
Mary I am afraid that Joe and Lila talk for something different...
When importing a resource (just this) from Course A to Course B, then you take by default the 'course-level customized question categories' from Course A to Course B.
Specifically:
Course A contains three question categories in course level:
- The Default for Course A
- Math questions (teacher added)
- Literature questions (teacher added)
Now, if you import a resource (not a quiz, just a single resource) in Course B you'll see the following structure in question categories:
- The Default for Course B
- Math questions
- Literature questions
See? Although we don't import a quiz, we do get the quiz categories (of the course level)... For those who work a lot with customised question categories and rely on import facility, the result is a messy question bank.
Although I haven't seen that behaviour prior to Moodle 2.+ (I currently work in 2.2) I am not sure if this can be considered as a bug or it's something "correct" according to the new concept of backup-restore.
Joe and Lila, a way to reuse your resources from one course to the other without carrying the question categories is to take a backup of the specific resource (from the editing page of the resource -> click backup, then restore this backup of the single resource into the course you want). This way you won't carry the question categories.
It's not very helpfull though if you want to take more than one resources... 
It would be nice to have the control over this (to be able to choose to import the quiz categories or not)... import is great facility...