diff -r 46bd94b12a0c lib/galaxy/jobs/schedulingpolicy/roundrobin.py
--- a/lib/galaxy/jobs/schedulingpolicy/roundrobin.py	Thu Jul 16 15:35:58 2009 -0400
+++ b/lib/galaxy/jobs/schedulingpolicy/roundrobin.py	Thu Jul 23 13:08:33 2009 -0400
@@ -34,7 +34,13 @@
         # locks for get and put methods
         self.putlock = threading.Lock() 
         self.getlock = threading.Lock()
+        self.job_lock = False
         log.info("RoundRobin policy: initialized ")
+    
+    def set_job_lock ( self, newstate=True ):
+        self.getlock.acquire()
+        self.job_lock = newstate
+        self.getlock.release()
 
     # Insert a job in the dict of queues
     def put(self, job): 
@@ -63,6 +69,9 @@
             # get the next user/session in the dict
             sessionid = self.__get_next_session()
             if sessionid is not None :
+                if (self.job_lock):
+                    log.info("RoundRobin queue: Job Lock active, returning: Empty" )
+                    raise Empty
                 log.debug("RoundRobin queue: retrieving job from job queue for session = %d" % sessionid)        
                 return self.__DOQ[sessionid].get()
             else :               
diff -r 46bd94b12a0c lib/galaxy/web/controllers/admin.py
--- a/lib/galaxy/web/controllers/admin.py	Thu Jul 16 15:35:58 2009 -0400
+++ b/lib/galaxy/web/controllers/admin.py	Thu Jul 23 13:08:33 2009 -0400
@@ -3,6 +3,7 @@
 from galaxy import util, datatypes
 from galaxy.web.base.controller import *
 from galaxy.model.orm import *
+from galaxy.jobs.schedulingpolicy.roundrobin import UserRoundRobin
 import sys
 
 import logging
@@ -2059,6 +2060,31 @@
 
     @web.expose
     @web.require_admin
+    def job_lock ( self, trans, **kwd ):
+        params = util.Params( kwd )
+        newstate = params.get('joblockstate', '')
+        messagetype = 'done'
+        msg = ''
+        job_lock_active = False
+        
+        #This is a bit ugly...
+        job_queue = self.app.job_manager.job_queue
+        if not job_queue.use_policy:
+            return trans.show_error_message ( message = 'Job lock requires "User-Round-Robin" job scheduler.<br/>Please change "job_scheduler_policy" settings in "universe_wsgi.ini"' )
+        sched_obj = self.app.job_manager.job_queue.squeue
+        if not isinstance(sched_obj, UserRoundRobin):
+            return trans.show_error_message ( message = 'Job lock requires "User-Round-Robin" job scheduler.<br/>Please change "job_scheduler_policy" settings in "universe_wsgi.ini"' )
+        
+        if newstate == 'enabled':
+            msg = 'Job lock enabled'
+            sched_obj.set_job_lock(True)
+        elif newstate == 'disabled':
+            msg = 'Job lock disabled'
+            sched_obj.set_job_lock(False)
+        job_lock_active = sched_obj.job_lock 
+        return trans.fill_template( '/admin/job_lock.mako', job_lock_active=job_lock_active, msg=msg, messagetype=messagetype )
+    @web.expose
+    @web.require_admin
     def jobs( self, trans, stop = [], stop_msg = None, cutoff = 180, **kwd ):
         deleted = []
         msg = None
diff -r 46bd94b12a0c templates/admin/index.mako
--- a/templates/admin/index.mako	Thu Jul 16 15:35:58 2009 -0400
+++ b/templates/admin/index.mako	Thu Jul 23 13:08:33 2009 -0400
@@ -101,6 +101,7 @@
                     <div class="toolTitle"><a href="${h.url_for( controller='admin', action='reload_tool' )}" target="galaxy_main">Reload a tool's configuration</a></div>
                     <div class="toolTitle"><a href="${h.url_for( controller='admin', action='memdump' )}" target="galaxy_main">Profile memory usage</a></div>
                     <div class="toolTitle"><a href="${h.url_for( controller='admin', action='jobs' )}" target="galaxy_main">Manage jobs</a></div>
+                    <div class="toolTitle"><a href="${h.url_for( controller='admin', action='job_lock' )}" target="galaxy_main">Job Lock</a></div>
                   </div>
                 </div>
                 <div class="toolSectionPad"></div>