There is a bug that changes the Garbage Collection settings when you change other settings on the page. If you have your Garbage Collection timer set and then change the exclusion strings or Rejected URIs and click "Save Strings" it will reset your Garbage Collection scheduler to "Clock" instead of "Timer".
Duplicate by doing the following:
- set Garbage Collection Cache Timeout
- select Garbage Collection Scheduler "Timer" radio button and enter a seconds value
- click "Change Expiration" button
- verify settings were saved
- check one of the rejected URI boxes
- click the "Save" button under those checkboxes
- Garbage warning will now appear and the Collection Scheduler will be rest to "Clock"
This can also be duplicated by clicking the "Save Strings" button which will reset the Collection Scheduler to "Clock"