They posted the problem as being under investigation
"Form 502: Other additions to code 1..." error when attempting to e-file Maryland return
This error message occurs when attempting to e-file your Maryland return. The full message reads:
You Must Fix This Error
Form 502: Other additions code 1, Other Additions Code Box 1, must be code A through O, or DM, to qualify for electronic filing.
However, the Other Additions Code 1 field on the screen shows a code O and the field won't allow input. This issue prevents you from e-filing your Maryland tax return.
This issue, which was first reported to us on the evening of Friday, February 2, is currently under investigation. If you would like to be notified via e-mail as soon as we have developed a fix or workaround, please click here to sign up.
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I've used Pro Series, Tax Cut, Turbo Tax in the past and this is the 1st time I've ever actually found an issue with the software.
BTW, I was the 1st user to report the problem. Aren't I special.