Microsoft&39's CEO Steve Ballmer shows off a slate PC at CES 2010.

Wall Street's confidence in Microsoft for next year has taken a hit, with what Goldman Sachs is attributing to the software giant's approach in both tablet PCs and mobile phones.

In a Goldman Sachs research note released over the weekend, picked up by blog Techflash, the firm says that Microsoft is due for a "more challenging year" and that the company's top-line growth (or revenue) could slow from 12 percent this year to 7 percent next year.

Microsoft beat expectations in its last fiscal quarter, pulling in $5.41 billion in net income, on revenue of $16.2 billion. The company also saw a 13 percent growth in sales, taking into account a deferral of revenue ahead of the release of Windows 7. Some of the factors Microsoft's CFO Peter Klein had attributed to the those numbers were strong sales of Office 2010, Windows 7, and the Xbox 360, as well as growth in the enterprise.

Despite that, the research note points to weaknesses in the company's tablet strategy, and mobile devices at large. "A tablet response is still not forthcoming and our early read on Windows Phone 7 has not yet changed our view that Microsoft's share in mobile OSes will remain at only the single-digit level," the research note said.

Microsoft has not yet released sales numbers on Windows Phone 7 devices, though it is expected to as part of the company's keynote speech at the Consumer Electronics Show next month. There have also been questions about if and when the company intends to bring that same experience to larger form-factor devices, like a tablet, to fit in things like instant resume and increasingly long standby times--two things Windows 7 cannot yet quite match.

In any case, Microsoft's continuing tablet strategy should come into more of a focus at CES, where last year's keynote speech featured a number of tablets, including HP's Slate 500, which had been rumored to be scrapped.