Microsoft has confirmed that some third party applications are either blocked or lose functionality on machines that have Vista service pack 1 installed, including products from Trend Micro, Zonelabs, BitDefender, and Novell.

In a Knowledge Base article published Wednesday, Microsoft said some applications "may experience a loss of functionality after you install Windows Vista SP1."

In the article, Microsoft notes that Trend Micro Internet Security 2008, Zone Alarm Security Suite 7.1, and BitDefender's AV and Internet Security products from starting on machines that have Vista SP1 installed. "For reliability reasons, Microsoft blocks these programs from starting after you install Windows Vista SP1," according to the article, which notes this step was taken with the consent of the affected vendors.

Ji-Young Kim, product marketing manager and director at Trend Micro, San Jose, Calif., says the security vendor has developed a pair of workarounds for the Vista SP1 compatibility issue.

With the 16.05 update, which is available now, Trend disabled a behavioral monitoring module in the software in order to avoid issues with blue screens, said Kim. The 16.1 update -- which restores the module and meets Microsoft's certification standards -- will be available in early March, said Kim. Both updates are being distributed through Trend's auto update service.

BitDefender also offers a free upgrade that fixes the problem.

Microsoft said a supported version of Zone Alarm Security Suite (7.1.218.0 or a later version) is now available. ZoneLabs couldn't be reached for comment.

Microsoft also said in the article that Novell's ZCM Agent 10.01 loses functionality and is not supported in Vista SP1, a somewhat ironic development in light of the two vendors' 2006 pact to build interoperability between Windows and Linux.

Microsoft directed users to a page on the Novell support website, but the page doesn't contain any information on what specific functionality is affected. Novell couldn't be reached for comment.