Sounds as if on of the spider's arms has fractured and is allowing the the inner drum to contact the outer drum in the fast spin cycle (when the unbalanced forces will be the greatest).
As you say the bearings seem OK please check for relative movement between the inner and outer drum. Please do this in four different possitions of the inner drum relative to outer. Should you get approximately equal movement in all four positions it would indicated that the bearing is the culprit, should however you be able to find one position where there is easily discernably more movement then this indicates you have a fractured spider arm. You may even have both, failed bearings and fractured spider. No prizes for that jackpot I am afraid.
When the bearings fail they take the seal with them, this allows water into the bearings, and 'rusty' water will dribble down the back of the outer drum from where the spider shaft exits in the centre, you could take the back off and have a look for this. As there is a considerable body of thought 'out there' that believe the seals fail first in the majority of cases, we have to allow that it is possible, however it really makes no difference to the end result, 'rusty' water, well laced with grease, will dribble down the back.
Please let us know how you get on.