I have a 1GB MicroSD sandisk that was once detected, but after I did some tinkering, formatting, etc. my e250R would no longer detect the disk. The disk was detectable in windows, and on my smartphone, but not on the Sansa. I tried several different methods of formatting, and was finally able to get it to work by using the following method (this was done on a Dell Inspiron 9400 built-in card reader with microSD to SD adapter) :
1) Download and Install the Panasonic SD Formatter: http://panasonic.jp/support/global/cs/sd/download/sd_formatter.html 2) Make sure your SD card is detected and start the SD Formatter program. Your drive should be detected in the program 3) Set options: Format Type: Full (Erase ON) Format Size Adjustment: On 4) click the format button and wait...
Once formatting is completed you can try inserting the disk into the Sansa and if it worked you'll see a quick database refresh and you can go to Settings > Info, and you'll see the memory listed for the SD.
If it still doesn't work put your microSD back into your computer and open up the Rhapsody player. It should detect the drive letter for your card. Right-click on the card and select "Format Device". I did a quick format.
Next copy a couple songs onto the device and then safely disconnect it from your computer (right click on device in Rhapsody and select "Disconnect".
Hopefully the disk will now work on your Sansa. It did for me!