From the error, it would seem that the routine RGRSUTIL exists but it does not have the line label EXCEPT.
If EXCEPT^RGRSUTIL exists, then look at the other items in the XU USER SIGNON EVENT.
If you are missing the EXCEPT line label, then I do not know what to recommend. I do not know how you got to the point where you are. My RGRSUTIL routine does have a line label EXCEPT. I would recommend getting a fresh copy of VistA from the VA's FOIA FTP site. If this one routine is messed up, what else is messed up on your system?