If you edit a race in the .hst/.m/.x, but don't give it a negative balance, does this result in a HACKER flag? If so, there's something else going on that doesn't necessarily imply a check for racefile legality. If not, then it's a check for nonnegative balance and outside of involved .exe hacking there's no way to fix it.

(Are you sure that the .hst doesn't keep both the original password (for the race checksum) and the current password (for Change Password) in separate locations? That could explain the password results, if you were only modifying the current password.)