Xcelsius 4.5 Error - Serial # Invalid

Two errors occur when I attempt to export a file into SWF. First I receive a C++ runtime error and then a "The serial # is invalid. Please enter a valid serial number." error appears on the screen. The program had been running perfectly fine (and exporting) with no errors and then without reason it began to throw the errors described above and terminates before completing the export. Any idea what may be happening here?