The security key is stored on the first line of the miame.ini file. The format of the line is:

SERIAL=####kkkk-kkkk-kkk-kkkkkk-kkkkkkkk   ;comment

#### is your serial number and the kkk… represents your security (or license) key.

The most likely cause of this error is that the line has become corrupted, due to either manual editing or some other mishap. It is also possible that the CONAME file (referenced by the CONAME statement in the miame.ini file) has changed, since its contents are tied to the security key. If you have your original license key written down, you can re-enter it (from the dot prompt) using the LICENS command. Note that if your miame.ini file appears corrupted, you may need to first manually clean it up before it can be properly updted. To do this, use your favorite text file editor and set the first line to:

SERIAL=0999NXXXXXXXXXXXXXXXABCD          ; license key

Make sure to include several spaces between the ABCD and the semicolon.