Up until today I've been able to update parts and come back into the assembly and all of the mates get updated.. Now when I update a part or a plane dimension or sub assembly a random mate will give me an error.. I haven't modified the face / plane of the part, just say the length.. When i go back into the assembly i have a sea of red error's relating to the part / assembly i just modified.. I'll delete the coincident mate that is giving me the error and redo it using the same face's making it coincident and presto, the same coincident mate is fine.. ?? Is there a setting under system options that magically turned off that might be giving me these issues..