In the words of Steve Jobs, Ballmer is a Bozo.
Gates is undoubtedly brilliant, a brilliant software engineer and a great person at heart. No matter your opinion on Microsoft you can't deny that Gates did a lot of good (and bad I suppose) for the industry, he knew his craft and knew very well how Windows fit into the personal computing marketplace and how it should go forward.
Ballmer on the other hand has seemingly played a CEO who doesn't know how Microsoft's products fit into the market and doesn't know how to push them forward, really he should be some pleb buried in a do-nothing middle-management position rather than leading the ship. His business strategy (or lack thereof), vision for the company and it's products and how Microsoft should grow comes across in all facets of Microsoft. From the half-and-half approach that the SDK has taken in recent years, Windows Vista looked like a project Ballmer oversaw and even the failure of product lines like the Kin & Zune. It's taken the rest of the industry to pull Microsoft forward and the result is a Microsoft that instead of leading the industries it does best in, is now following the competition and occasionally trying to be different for the sake of being different.
The solution is one that's apparent of everyone except the the stakeholders of Microsoft itself, even their employees and possibly Gates himself (I'm guessing here) have deluded themselves into thinking that Ballmer is at all capable of running Microsoft.