Hi,
Believe it or not I have a washer just like yours and when that happened to me I found that the shocks that hold the drum were broken. I ordered new shocks online and replaced them and everything was fine and dandy again!
The shocks are a bit of a pain to install but not all that difiicult.
Do a search for "appliance parts" online and then enter your model number and you can easily find and order the shocks you need.
Check out different sites as the prices can vary for the same part and it seems that there is not any one site that always has the lowest price.
The new shocks also seemed to be built differently then the old ones. (heavier)

I hope that this will help you to solve your problem!

Thanks for using Fixya!!

Heatman101