I just found out that my Feb. 2008 cruise on Liberty is cancelled.

They're going into dry dock for two weeks.
We've tried to find another 6-day on Carnival within those dates, but weren't able to. We really want to be on the water on Feb. 29th. Our daughter is a "Leap-Child" and will turn 4/16 that day.
We ended up with a 5-day on RC Navigator of the Seas.
Does this happen often? I was so excited to book another (longer, bigger ship) cruise with Carnival so quickly after coming home from my first.
Edit: There already is an active thread on this topic here. Please continue there. Thank you. RF