Ah, yes, I should have posted this in the Developer's forum. Sorry.
After 45 minutes on the phone and a call-back half an hour later when I'd updated the system, the CS gentleman decided to try something: he turned on special offers,and then turned them off again. Like magic, they were gone... which indicates that the problem was on their side, not mine (thank heavens. This is the first time I've ever jailbroken a kindle, and if that had been the problem, I would have been very upset).
As part of our troubleshooting, I did have to update to 5.3.3... that shouldnt' mess wth the jailbreak and collection manager, should it?