Microsoft last night announced that it was delivering a "wave" of firmware updates to Windows Phone handsets, aimed at fixing bugs in certain models. As important, the company is now delivering Windows Phone 7.5 to users of the Samsung Focus with firmware revision 1.4, a particularly difficult version of the phone that often has trouble getting updates in a timely manner. And there's also a new update to build 7740 for certain phones that fixes bugs with voice mail bug and Exchange 2003 support in Windows Phone 7.5.

With regards to the bug fixes, Microsoft didn't provide any details. But I've heard from two HTC HD7 users who claim the update fixed an audio issued they'd been experiencing since receiving Windows Phone 7.5, so I presume that was one of the fixes.

"These updates improve the overall function of your particular make and model of Windows Phone," Microsoft's Eric Hautala wrote in a blog post while declining to identify which phones are receiving these updates. "You'll see these firmware updates from time to time; they're easy to recognize because the update information in the Zune software shows your device name. If you get one, I encourage you to install it."

The Samsung Focus issue is interesting, as a Microsoft executive told me last month that it was caused by a software certificate that appears only on that revision of the handset. Whatever the cause, users with the 1.4 revision of the Focus firmware are usually the last to get updates, and that's certainly been the case with Windows Phone 7.5, which went out to most other phones a month ago. The related Samsung Omnia 7 in Telefonica in Spain has similar issues, but users of that device will soon be getting Windows Phone 7.5, Microsoft says. That should be everyone.

Finally, Hautala described a second post-Windows Phone 7.5 bug fix update, which increases the build number to 7740 (from WP7.5's 7720) and fixes two widely reported bugs with voice mail on Vodafone, Orange, and Deutsche Telekom in Europe and with Exchange 2003 support. According to the Windows Phone Update History page, Update 7.10.7740.16, as it's called, is currently available only in certain markets.