I had that one. We always joked that our washing machine was lifting off to Mars to wash the clothes there. The reason is simple: the bolts holding the concrete damping blocks in place are loose. You need to open the top of the washing machine and tighten all bolts (there are concrete blocks in top and bottom of the drum, with I believe 6 or 8 boltsin total). That should solve it.
Tony
January 2008