I can the D+B menu, which seems to be good news, but the maintenance menu will not come up when I power on using using the OK button combo. I've tried restoring the NAND ROM using my last NAND backup made with the D+B menu and the file provided on Trisoft, but the problem persists. Any suggestions?

use compact flash cards, not sd? eject all cards.

and if that fails there is always the dm menu