Sounds like your player had a hacked memory chip. By formatting the player you have removed the hack and now your player is showing it's true memory size of 256MB less memory taken up by the players firmware.
This is why you were getting error reports, any files transferred over the chips real size are written to memory that does not really exist. This is a common scam with these players, if you browse the forums you will find many posts on others who have been deceived by unscrupulous sellers.
To be sure you would need to open the player and check the memory chip serial number. There is a thread on how to identify the capacity of Samsung and Hynix memory chips here:
http://www.mympxplayer.org/samsung-a...rs-vt1692.html
Where did you purchase the player?