SLES 11.1 x64 servers, Win XP Pro Sp3 x86 workstations

After updating our primary and 5 satellite servers from 10.3.3 to Zenworks 11.1a, the agent deployment has turned into trickle. The update windows is daily from 6 am to 4 pm. The first day of deployment, about 400 of 1000 machines successfully updated. Then, 200 the next day, then about 80 the next. After 2+ weeks only about 650 of 1000 computers have updated. Only several machines per day now update. Neither refreshing from the workstation nor via ZCC will trigger the 10.3.3 agents to update. Clearing the cache didn't help, not did "zac ref bypasscache." All the 10.3.3 agents just say pending in ZCC> Configuration> System Update. I canceled and re-deployed to update, but it didn't resolve the issue. I ran across a post (can't find it now) for a similar problem with 11.1 to 11.1a. It was a bad/missing file in %Zenworks_home%\bin. It doesn't seem to be the issue in 10.3.3 on our machines; I'd check again if I could find the post.

Re-registering them may work, but I'd rather not do that. And uninstalling the old agent and reinstalling the agent isn't timely enough.

Any suggestions?