the problem here is that some RKW firmwares have some deep boot code in them that can set up your player incorrectly for thew original firmware
you see for some updates you can do it on the player, for more complex updates where some major code has changed that alter the boot record of the player the tool is needed
in this case you have loaded RKW files that have changed some core boot code in yur player and this is why you now can not use your original files
all i can suggest is you try other RKW files, maybe an older rkw from a few months back through the tool and then try to copy over your files
also if all else fails you may need to do a hard reset by opening the player and shorting out the memory chip, this may clear out the player completely
also try this tool, its a cleaner tool to clear up the hidden partition, try it on your player then copy back your original files
a tutorial is here
http://www.mp4nation.net/forum/viewtopic.php?f=6&t=7737
the tool is called the onda cleaner tool, it cant hurt to try