SonicWall officials said that the server "malfunctioned," leading it to reset the license keys for products installed on customer systems. That made the licenses appear to be invalid, requiring users to resynchronize them with the vendor's license management system after the glitch was resolved.

The incident prompted numerous customers to post angry messages on a support forum maintained on SonicWall's Web site. (The forum can be accessed from the company's main but requires registration.) Several of the postings expressed frustration at the fact that a problem with a license server had managed to take down essential security services for customers with fully valid licenses.

An IT security administrator, who asked not to be identified, said Friday that his organization won't renew its contract with SonicWall, worth more than US$50,000, at least partly as a result of the server glitch.

"I do see a lot of their customers jumping ship over issues like this," the admin said. He added that there are "a dozen different ways" for vendors to license products without resorting to the "Draconian" real-time license-validation scheme that SonicWall has adopted. The company's use of a remote-kill feature to shut down security services on customer systems is "completely unacceptable," said the admin, who described Astaro's 50% discount as interesting but didn't say if his organization would take advantage of the promotion.

SonicWall officials didn't respond to a request for comment on Astaro's trade-in offer before this story was posted.