What is the "Duplicate Provider" error? I have installed Angry birds from the official android market. I tried installing the Angry Birds Seasons free version today, and while installing I got a pop-up message saying "Duplicate provider" and the installation terminated. I am running ICS on Nexus S, if it's relevant.
That means something's wrong with the package setup. For your reference, here are a few links with more detailed information:


android duplicate provider authority - Stack Overflow
Android duplicate provider authority problem - Stack Overflow
Angry Birds Seasons Summer Pignic Now Available | AngryBirdsNest (search for "duplicate provider" on this page, should appear around the middle)
Duplicate provider authority error when installing K-9 mail - Google Groups


Recommendation: Contact developer (for security reasons both developers, in case somebody faked the signature). It's most likely a copy-and-paste error during the packaging process, so the developer might release a fixed update soon.