poking around the interwebs i found this:
"On April 1, 2010, scan.exe in the daily SuperDAT was replaced with a small stub file of the same name.
With the End Of Life for the V1 DATs on March 31, 2010, the Command Line Scanner (scan.exe) has been removed from the daily SuperDAT packages (sdatxxxx.exe and xdatxxxx.exe). For compatibility reasons, a stub file named scan.exe will remain in the SuperDAT packages. However, this is is not an actual executable file."
this matched up with the time that things started breaking for me.
the fix is to take the files scan.exe, scan.dat, license.dat, messages.dat, names.dat, mcscan32.dll from an older working version of the command line scanner and drop them into your new folder.
putting this here in the hopes that someone else doesn't have to slog through a bunch of people's "are you sure you're doing it right?" responses.