UPDATE 1-US software maker files complaint vs IBM with EU

(Adds IBM statement, dateline SAN FRANCISCO)

BRUSSELS/SAN FRANCISCO, Dec 18 (Reuters) - Software maker Platform Solutions Inc has filed a complaint with the European Commission alleging that IBM (IBM.N) abused its market dominance by refusing to share information related to its high- performance mainframe computers.

The complaint, filed on Oct. 19 according to a European Commission spokesman, is the latest in an ongoing intellectual property dispute between privately held Platform Solutions and International Business Machines Corp, the world's largest technology services company.

Platform Solutions alleges IBM violated an EC prohibition on abuse of market dominance by refusing to supply interface information relating to mainframe computers and refusing to license third parties, commission spokesman Jonathan Todd said in a statement.

The commission is in the preliminary stages of examining the complaint, Todd said.

IBM, based in Armonk, New York, said it would be "bringing Platform Solutions' intellectual property violations to the attention of the commission as well." It added in the statement that it is "confident that the commission will protect IBM's property rights and reject PSI's claims."

The EC provision against abuse of dominance was central to the commission's landmark antitrust court victory over Microsoft Corp (MSFT.O) in September before a European Union court.

It was also used for a major settlement between Brussels and IBM in the 1980s, in which IBM promised to provide interface information for its mainframes.

The complaint by Platform Solutions is the latest in a tit- for-tat series of legal moves by the two companies.

In December 2006, IBM sued Platform Solutions charging that the company, which manufactures software that can run on IBM's high-end systems, violated patents IBM holds on some of its operating systems.

In January this year, Platform Solutions counter-sued, alleging IBM engaged in unfair competition. Platform Solutions also denied it had violated IBM's patents. (Reporting by David Lawsky in Brussels and Philipp Gollner in San Francisco; Editing by David Holmes/Andre Grenon)