A week and a half ago, online reports about an internal countdown clock at Microsoft verified my early 2006 report that the software giant was pushing for an October 25 Windows Vista release to manufacturing (RTM) date. But last week, Jim Allchin, co-president of Microsoft's Platforms and Services Division, admitted that the company had run into a snag and that Microsoft wouldn't make its planned RTM date. As of today, however, Microsoft is back on track because it has a working Vista build in escrow.

In an interview with Mary Jo Foley at "ZDNet" last week, Allchin said that Microsoft wouldn't be able to release Vista to manufacturing by October 25. "We are in pretty good shape," Allchin told Foley. "And there are still months before (the January 2007) launch."

Allchin was alluding to an internal timetable that I previously reported on in WinInfo: He had told the Windows Division that Microsoft could afford to postpone Vista's RTM date to as late as November 8 and still meet its November and January launch dates. However, each delay comes with a price, Allchin said: For each day past October 25, Microsoft will ship one fewer localized, language-specific version of Vista in the January launch.

I've found out that the source of Allchin's concerns was an unexpectedly buggy pre-RTM build of Vista. The previous Friday, Microsoft pushed Vista build 5824 into escrow, hoping that the build could qualify as the final shipping version. But a catastrophic problem with the build destroyed any systems that upgraded from Windows XP, requiring complete reinstallations. After several frantic days of trying to find the bug, Microsoft finally fixed the problem last Friday and reset escrow. On Friday, Microsoft internally released build 5840, which didn't include the bug. Testing over the weekend produced positive feedback.

Vista build 5840 includes a surprising number of brand-new and final icons, and a new set of final wallpapers, including a default wallpaper that's a variation of the Aurora "swoosh" that Microsoft has been using as a Vista identifier since it announced the branding in July 2005. There aren't any major functional changes in this build.

Oh, and that internal countdown clock? Last week, it was reset to count down to November 8, not to October 25. It's not clear, however, whether Microsoft will release Vista to manufacturing before November 8, and which--if any--language-specific versions of Vista will be dropped.