As elkitten says, it sounds like the type of message where you may have already lodged an application or a visa has been issued against the same passport number.
If you're overseas, you can always send in an email to enquire and put in your passport number and they'll check the system to see if someone has a fake passport with your number and that kind of stuff.
i haven't lodge an application before. But my wife did in 2007 in which i appeared as the dependent. Case officer has not been assigned to this application yet as her occupation is not in the demand list. that was the reason behind me applying as the main applicant in fresh.
could this be the reason? but as i know anyone can make any number of applications and since i was the dependent in the previous this should not be the case.
i sent an email inquiry but the respond was some generic stuff.
I think that very well may be why you are getting an error message....
When I applied for a WHV years ago I had a massive problem with an online form (it was asking me when i left the country which i was currently living in since it was not the same country as my passport...i obviously hadnt left, couldnt enter a future date and chaos ensued...). The only way i fgured it out was by going to see an embassy person...in person at the embassy....
So i reckon you need to call the visa information hotline or lodge your application in paper. There isnt much they can do if it is the programing that is stopping you from applying though.... call the hotline they might be able to direct you.