hey yeah i had the same problem with my sansa e250r. when mine does that i
1. turn it off
2. put the hold button on
3. hold down the rec. button
4. turn it back on
that will get you into recovery mode connect your data cable once you have hooked it up to your computer open my computer and you should see a 16mb drive there instead of your normal mp3.
once you see that open it up.
now go to http://www.sandisk.com/Retail/Default.aspx?CatID=1449
scroll down and click on download firmware link
once you have downloaded that file unzip it and copy the file that is inside to the 16mb drive that you opened up in my computer.
once you have done all the above,,
1. take the hold button off
2. disconnect the data cable
3. wait for it to reboot.
if the above dosent work you might wanna take it to the dealer.
hopefully this works for you as well as it did me. good luck