Before I start to code this I just wanted to ask: is it possible to create a shopping price rule that will disable catalog price rule calculations?
Catalog price rules an cart price rules are independent.
The catalog rules are parsed separately via the price index and recalculated every night.
The final price of a product may or may not be influenced by a catalog rule.
The cart rules, don't care where the final price comes from. they just use it. So there is no way to determine if a catalog rule was applied to the price and disable it on the fly.
Also you cannot increase prices (not by default at least) by using the cart rules. You can only decrease them.
The idea came from Marshall Thornton' blog: http://www.magentotips.info/modules/catalog-shopping-cart-pricing-rules-stacking/#.VmIev98rKV4
Basicaly you need to extend Mage_SalesRule_Model_Validator::process() method