The news came out and about through AMD's filing with the Security and Exchange Commission in the US. The SEC filing claims that Intel "(i) alleges that the Company has committed a material breach of the Cross License through the creation of the Company's GLOBALFOUNDRIES joint venture and (ii) purports to terminate the Company's rights and licenses under the Cross License in 60 days if the alleged breach has not been corrected".
AMD sees things a little differently, and states that it has not broken the agreement - but that Intel's attempt at terminating the agreement is in itself a breach of the agreement. Brace yourself, as AMD "explains" that "Intel's purported attempt to terminate the Company's rights and licenses under the Cross License itself constitutes a material breach of the Cross License by Intel which gives the Company the right to terminate Intel's rights and licenses under the Cross License Agreement while retaining the Company's rights and licenses under the Cross License Agreement". Finishing all four campaigns on expert in Left 4 Dead is easier than reading that sentence aloud.
An Intel spokesperson said that "Intel believes that the formation of Global Foundries is not a subsidiary under terms of the agreement and is therefore not licensed under a 2001 patent cross license agreement and that AMD violated the agreement." He added: "Intel does not believe AMD can unilaterally extend Intel's rights to a 3rd party without Intel's consent."
The two companies have never exactly been friends, and are still in an antitrust battle in the EU. It's anybody's guess as to how serious this recent threat is.