I'm assuming it is the mount on the gearbox? Touratech do a plate specifically to beef up that area I think, not that that's any use to you at the moment. I was with a rider who had this happen outside Bamako and another on an R850 just outside Anchorage. We got a huge lorry tie down on the 1150 and strapped the seat down to take the pressure of the spring. It was just about ridable like that. Welding is the only solution by the sounds of it + get someone to make up a support plate that bolts on to one of the footrest hangers too to spread the load.
see
http://www.ascycles.com/detail.aspx?ID=2136