I'm guessing you are printing a 'form' (Invoice Printing, Sales Order Printing, Picking Sheet Printing, etc) instead of a report. On the parameter screen, click on the FORM button. Descrease the page length setting.
Basically, you are printing too many lines for the page. The printer is generating a form feed when you've reached the end of it's page & then MAS90 is sending a form feed when it's finished with it's page -- the result is a double form-feed & you then see the every-other-page sitatuation that you've described.