Update: The U.S. Court of Appeals for the Federal Circuit has reportedly granted Microsoft's motion to stay an injunction that would prohibit the software giant from selling Word. The injunction had an effective date of Oct. 10, but the motion to stay blocks the injunction until the appeal process is complete, according to The Microsoft Blog.
Original Article: A Texas judge has reportedly ruled that Microsoft cannot sell any version of Word in the US that can open .XML, .DOCX or DOCM files (XML files) containing custom XML. Seattlepi's Microsoft Blog points to an announcement by the plaintiff, i4i.
In May, i4i in Toronto got $200 million from Microsoft, when a federal jury found that Microsoft infringed on the company's patent. That patent is 11 years old. The abstract reads:

The entire thing can be read here.
"We are disappointed by the court's ruling," a Microsoft spokesman is quoted as saying in a statement. "We believe the evidence clearly demonstrated that we do not infringe and that the i4i patent is invalid. We will appeal the verdict."