i4i Limited Partnership, et al. v. Microsoft, US Court of Appeals for the Federal Circuit, December 22, 2009 [affirming a lower court ruling that Microsoft infringed on a patent of Canadian company i4i with portions of its Word 2007 word-processing software].
Reported in JURIST's Paper Chase here. Latest commentary available here. JURIST has more on various legal problems Microsoft has dealt with in recent years.