It looks that Opera browser caches pages which should not be cached. Example:

• go to Hudson->Manage Hudson-System Configuration
• change '# to executors' from 2 to 5
• click 'Ok' - the configuration will saved, you will be redirected to main page
• go to Hudson->Manage Hudson-System Configuration again - '# of executors'
  will be 2 again
• force page refresh - '# of executors' will be 5

Maybe putting some html headers ('No-Cache' or similar) could fix it.

Opera 9.21, Ubuntu 7.04