Clash of the GPL and Other IP Agreements?

Daimaou asks: "A situation I'm involved in at work has raised some questions regarding the GPL vs. IP agreements. When I started working for my employer several years ago I signed an IP agreement that states anything I think while working for them is theirs, as well as anything I've ever thought in the past if it enters their building; dumb, but I needed a job." To make a long story short: Daimaou wrote some code derived from GPLed sources. Now his company wants to take control over what he's written. IP agreements aside, this sounds like a GPL violation since the company's IP can't override IP already established by the original GPLed code. Daimaou also says the company is trying to patent at least some of the code. Is there anything Daimaou, or anyone else for that matter, can do to get the company to cut short their plans and play fair with IP that obviously doesn't belong entirely to them? "About a year and a half ago, I brought in some source code that I had worked on prior to working here; after receiving verbal OKs that the code would remain mine.

My code was derived from code I got from IBM's Developer Works website and also ActiveState's website; all of which was released under the GPL. I made a lot of additions to the software of my own, but the parts from the above sources were integral pieces and without them, my code wouldn't work.

Now, my employer is trying to lay claim to this software and has filed at least one patent on it that I know of. They have also distributed it but refuse to make the source public. They claim that because of my IP agreement, they have full rights to this source code.

I would like to hear what other readers think and perhaps get some suggested courses of action from people who are smarter with regards to law and the GPL than I am."