Recently, I've been unable to use my (already registered) credit card with the Ovi store. I used it back earlier this year to buy the Angry Birds Level Pack without problems. Now I'm unable to re-use it again to buy Morpho Panorama.
(Haven't yet checked if deleting / re-registering helps)

The teething problems of the Ovi Store are just unbelieveable. Every baby learns quicker. The search/browse interface has an absurd filtering mechanism.