(FORTUNE Magazine) – Last month, when Microsoft announced its bellwether decision to award employees restricted stock instead of options, it also made news in a federal courtroom--the kind of news you keep quiet about.

Microsoft suffered utter defeat at a crucial pretrial hearing in what appears to be the highest-stakes patent litigation ever--one in which a tiny company called InterTrust Technologies claims that 85% of Microsoft's entire product line infringes its digital security patents. (See "Can This Man Bring Down Microsoft?" on fortune.com.)

InterTrust's engineers developed and patented what they say are key inventions in two areas: so-called digital-rights management and trusted systems. The technologies are essential to the digital distribution of copyrighted music and movies, and to maintaining the security of e-commerce in general. At its prebubble height, InterTrust (founded in 1990) employed 376 people and marketed its own software and hardware products; today it consists mainly of a patent portfolio, 30 employees, and this lawsuit. An investor group led by Sony Corp. of America and Royal Philips Electronics bought the company in January for $453 million, hoping to convince consumer electronics and tech companies--beginning with Microsoft--of the need to license its patents.

Microsoft argued in court that crucial phrases in InterTrust's patents were too vague to be enforceable, and that others required such narrow interpretation that they would have been hard for Microsoft to infringe. But in her July 3 ruling, an Oakland judge resolved 33 of 33 disputed issues against Microsoft and rebuked the company's lawyers for wasting her time by promising proof that never materialized--legal vaporware, in essence.

"This is simply another step in a long legal process," says a Microsoft spokesman, putting the best face on it. "Microsoft will continue to defend itself against what we believe are groundless and overbroad claims."

As agreed before the hearing, the parties now enter a round of settlement talks. Though InterTrust declines to place a pricetag on the suit, it's hard to imagine the company settling now for any sum that does not have a "B" in it. InterTrust claims that its inventions cover technologies that Microsoft has been weaving into its Windows XP operating system, Office XP Suite, Windows Media Player, Xbox videogame console, and .NET networked computing platform, to name just a few. If settlement talks fail and InterTrust prevails in court, it would be entitled to a court order halting sales of all those products. InterTrust CEO Talal Shamoon asks rhetorically, "How much would that be worth to Microsoft?" --Roger Parloff