Windows Phone 7 made its much awaited debut on AT&T yesterday, but not without its flaws. The Samsung Focus seems to be having reliability issues with the microSD cards that shipped with the phone. AT&T employees are being told not to install the cards in the phones in-store and that buyers need to wait before installing. If you have it installed and working already, you're lucky but not alone, and don't remove it. Microsoft is working on a patch that should fix any issues with the SD cards and until then, if you have a Focus, refrain from using the card.
Originally, Mircosoft said that Windows Phone 7 didn't support microSD cards. WP7 does supports microSD cards, but it has very specific requirements for a card to work with the OS:
"The SD card in a Windows Phone 7 device must meet certain performance requirements for the phone to function optimally. If the SD card does not meet these performance requirements, the phone will have portions of memory that meet the performance needs of the operating system (the internal storage) and portions of memory that do not meet the needs of the operating system (the SD card). This can lead to poor and unpredictable performance when using the phone. This article uses the term Windows Phone 7 compliant to refer to SD cards that meet the performance requirements for Windows Phone 7 devices.
Determining whether an SD card is Windows Phone 7 compliant is not a simple matter of judging its speed class. Several other factors, such as the number of random read/write operations per second, play a role in determining how well an SD card performs with Windows Phone 7 devices."
You would think that Samsung would know these requirements and have everything squared away for launch, but apparently they didn't. Windows Phone 7 is here, and it's off to a rocky start. I'm sure we'll be hearing more from this WP7-microSD debacle in the near future, and this patch should be out fairly soon, so stay tuned.
Source Windows Phone Secrets