Last weekend on the way back from Lubeck with Ryanair we were not allowed to sit in the first six rows nor the last four rows of the plane due to "balance" issues. This has been Ryanair's excuse for practically every flight that I have flown with them. However on this occassion there was a problem with the plane and after about an hour we had to disembark because the pilot was having a problem with the hydraulics. Eventually the problem with the hydrolics was sorted and we were allowed back on the plane after about an hour. However as we were boarding we were told to sit anywhere on the plane so that we could take off as soon as possible. How come there was a problem with "balance" when we first boarded the plane but no problem when we boarded the second time?