Hello I have a problem with my Sansa E250. I have had it since last christmas and have only had some problems with it (random reboots) but they have since stopped. Now, however, when I plug the player into the USB cable, it boots up, mounts itself, then immidiately rebbots, and continually does this process until I unplug it. I tried to plug it in without the the battery and the same thing happens. If someone could help me it would be much appreciated.
If your player is a regular e250 try what I said in this thread Here.
Perhaps you changed the USB mode by accident?
Make sure it is what you set it to be (MSC or MTP)
OTherwise, Make sure the Firmware is the newest, format and reload. hope this helps!