Microsoft co-founder Paul Allen’s patent suit against AOL, Google, Yahoo and Apple has been brought back to life by a federal appeals court, which disagreed with a judge’s earlier finding that the companies didn’t violate a 14-year-old patent held by Allen’s now-defunct Interval Research lab.

AOL, Apple, Yahoo and Google had contended that the language of the patent covered only situations in which information was displayed on background wallpapers and screensavers. Interval argued that the patent also applied to common “pop-up” notifications.

U.S. District Judge Marsha Pechman had sided with AOL, Apple, Yahoo and Google on that question, ruling that the pop-up notifications didn’t violate the patent, but the U.S. Court of Appeals for the Federal Circuit ruled Wednesday that the judge was reading that patent too narrowly. The court upheld other aspects of Pechman’s ruling.

Interval Research was a Silicon Valley lab that Allen created with Xerox PARC veteran David Liddle in the 1990s. The original suit was filed in 2010 against a wide variety of companies, citing Interval patents that reflected the lab’s early role in developing fundamental approaches to browsing, displaying and alerting people to information online.

The case has illustrated the struggle some judges face in complex tech patent cases. “What I know about computers is really minimal,” Pechman told the lawyers in the case during a 2011 hearing. “If you want me to understand these patents then you’ve got to start educating me.” She advised them to treat her as if she were an intelligent, teachable eighth grader.

The appeals court, in its ruling Wednesday, sent the case back to Pechman for further proceedings consistent with its interpretation of the patent. Read the full decision here: PDF.