Neal may be right, but it might not take anything so drasitc. If you are trying to distribute to a robot under a different hub than the one the distsrv is on, you could try deleting the security.cfg file as Neal suggested. But you could also just compare to make sure both hubs are using the same security.cfg file. A couple of other possibilities also come to mind when dealing with SID errors...
You might want to try a fresh login to the Infrastructure Manager. If you do this from the Security menu, you do not even need to reenter your password. That will definitely get you a fresh SID.
It may be possible that this error indicates the distsrv does not have the needed permissions. From the Security menu, select Probe Administration. Make sure the distsrv appears there. I think the distsrv requires admin privileges.
-Keith