The only thing you can do is use DFU there.
If you have a computer with Windows Vista, that should be the simplest and you should be able to simply copy the CORRECT SL firmware files onto your player there.
If you use Windows XP, search on the forums for the DFU tools for SL, and try using that. To get a thorough guide on using DFU tools, please see the FAQ, however do NOT try to use the DFU tools normally spread around as those are for the TP and SP version of M6. Again, you need the DFU tools for the SL version, found on the forums

Good luck, no worrys! That doesn't help.