Here’s a lesson right out of the keep-your-enemies-close playbook. Nuance Communications filed a patent infringement lawsuit against Zi Corp. over SMS technology just days after it rejected the Burlington, MA-based company’s all-cash $40.5 million takeover bid. Nuance and its Tegic subsidiary said it filed suit against Zi in a federal court in Toronto claiming Zi’s Qix and eZiText products infringe on Tegic’s intellectual property, particularly Canadian patent Nos. 2,399.961 and 2,278,549 – both of which are titled “Reduced Keyboard Disambiguating System.” Nuance acquired Tegic last June. (Nuance Release).

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Zi fired back its own press release that said the motion accuses Zi of violating a 2002 settlement over patent litigation with Tegic. Zi President and CEO Milos Djokovic: “This motion for contempt is without merit. Providing this notice is clearly a tactic employed by Nuance in light of its failed proposal to acquire Zi last week at a low valuation. The timing of this motion is highly suspicious and is an unnecessary legal tactic by Nuance. We are disappointed that Nuance is resorting to these kinds of tactics to acquire Zi without recognizing its full value. We will vigorously defend ourselves in this litigation proceeding. We are examining all legal remedies available to us with respect to Nuance’s tactics.” (Zi Release).