The handset industry's conversion to open source OS threatens the steady gains made by Windows Mobile.
After nine years of effort, Microsoft is in third position in smartphone OS behind Nokia and RIM.
The latest figures from Gartner show Windows Mobile shipped in 3.87 million handsets in Q2, up from 3.21 million in the same period last year.
That's a 20% gain - well ahead of the 16% growth in the total market, while market share improved from 11.5% to 12.0%.
Which is all to the good, but the game is moving away from Microsoft.
When it comes to apps, its strength is in the Office suite. That suits BlackBerry users, but not the flood of consumer users buying 3G smartphones. They're installing maps, games and niche apps on their mobile phones - not Office and Acrobat.
But how much longer can Microsoft keep charging license fees to handset manufacturers of between $8 and $15‾
The handset platform market has suddenly gone open source this year. With the arrival of Google's Linux-based Android, Nokia decided to open up Symbian to all.
Microsoft has said it has no plans to eliminate license charges, which is understandable; free just isn't the Microsoft way.
But I wouldn't bet against a license cut pretty soon. Right now that extra fee is just one more incentive for OEMs to go with one of its rivals.