Well, if the system menu works, then it seems unlikely to me that it is a software problem. That doesn't explain why bootmii is not working though, although it could be that your SD card got damaged during this incident, causing bootmii to be unable to load the required files from the SD. That is one of the few explanations I can think of. Try using another SD card with the bootmii files on it, to see whether that makes any difference.
Anyway, it seems to me like a hardware problem. I think you were 'lucky' and only the cables got damaged. Try borrowing or buying new ones to see whether they do work.