Billing date correspond to 2030, why?

When a billing documen is saved shows an error regrading to an incosistency between the document date (29.04.2013)) and the last assigned date (29.04.2030).

To correct:

I enter in the header and change the billing date and in the level item, Serv. rendered date was change, too.

Both dates 29/04/2013.

After that, document pass to FI.

But this is just a partial solution, becuase the system continues getting the year 2030, for all invoices generated, since yeasterday.

This is so strange for me.

I've read some of your comments in other answers and I've reviewed dates, and all seems to be ok.

I'm a basic user, So, I'don have access to customizing things

The keyuser don't have any idea =(

For now, we are just correcting manually this invoices to be able to pass to FI

Please, help me into this strange issue.

Thanks!