yes i have the same problem, im not sure what is causing it yet, i have a broken motor mount and i believe the engine is twisting and changing the pinion angle for the drive shaft. if you have a broken mount let me know
check the clutch fork.....their is a spring that holds the throw out bearing to the fork i have seen that spring break or the throw out bearing some how come out of it
to eliminate a head gasket as a cause do a block test, kit is avalible at local part store. if it fails the test it is most likley a head gasket or a crack somwere. doing a block test your looking for exhaust fumes in the cooling system