Mr SizzlingSteak,
I can confirm the following for you:
1) I have an M3 Simply card.
2) I just "acquired" a version of Henry Hatsworth EU - 3540 to try it out for you.
3) It works just fine.
4) Member Golin is a LEGEND!
So, if you have a real M3 Simply and a good version of the rom *ahem* then I can only ask you to first try putting YSMenu onto your simply card and trying again. If that doesn't work you either have:
a) A copy card
b) A bad dump of the ROM - in which case look for another version
c) A bad Micro SD card
So, here try GOLIN's guide for YSMenu onto M3 simply
1. Go here:
http://home.usay.jp/pc/etc/nds/
2. Scroll down the Japanese page--it won't be on the Engrish version--and download YSMenu
3. Rename the compressed file to: YSMenu0810211800
4. Move the file to a newly created folder on the Desktop named: M3DSS
4. Download this:
http://62.50.15.93/~koen/hbdb/YSMenu/002/r4ysauto.zip
5. Extract file to the M3DSS folder on the Desktop.
6. Download this:
http://62.50.15.93/~koen/hbdb/YSMenu/002/update.zip
7. Extract file to the M3DSS folder on the Desktop.
8. Run r4.bat (it will update) and it will generate the .DAT file and TTMENU folder.
9. Move the new files to your M3 DS Simply... viola. (Move and Replace all--which is 2 files)
10. Turn it on and you'll be booting into YSMenu on your M3 DS Simply.
Good luck and enjoy!