Microsoft has issued a Surface Pro 2 update to fix glitches introduced by a December firmware release, which reduced battery life and changed how the device went into or out of sleep mode.

After releasing the December 10 firmware update that caused the problems, Microsoft pulled it, but not before some users had downloaded it.

”This weekend we released an update that addresses the unexpected wake and battery drain behavior experienced by a small number of Surface Pro 2 customers who installed the December Windows Update,” according to a statement sent by Microsoft’s public relations firm, Waggener Edstrom Communications. “This should have no impact on customers who had not received the December update.”

Microsoft is also moving to get the new update out to the users who never ended up installing the buggy December update.

”We are working hard to deliver the rest of the December update to those customers who had not received it prior to it being removed from distribution,” the statement said.

Earlier patch was no fix

The December 10 update caused some Surface Pro 2 users to report that battery power was draining faster than before, that the tablets were not fully charging or that they were not showing that they were being charged.

Other users reported a variety of wake and sleep issues, saying the devices shut down completely when the cover was closed, rather than going into power-saving sleep mode; or that the machines would not go into sleep mode even when the cover was closed.

This is not the first time Microsoft has pulled a Surface update. In October, the software giant removed from distribution a Windows RT 8.1 update after some Surface RT owners said their machines were freezing up.

Microsoft debuted the Surface 2, with the Windows RT 8.1 OS, and the Surface Pro 2 with Windows 8.1, in New York in September and released them commercially in October. The Surface Pro 2 is intended to be a PC replacement, and a thin keyboard accessory gives it a laptop-like feel.

With the PC market slumping and the tablet market growing, Microsoft is banking on the Surface line to help buoy revenue.