After the format you might be missing files for operating the device.
Formatting the player is normally used before updating the firmware.
Have you been updating the firmware after you formatted the player ?
There is a new firmware release for the MP610.
Look in the support page
, enter MP610
in the bar (Product Search) of next site:
Download the zip file. Unzip the downloaded file with WinZip or WinRar.
Look in the pdf file for the instruction
how to use the exe file for the