I have been trying to reproduce this on my own system, but have not been able to. These are the steps I took:
1. (Fresh install of Windows XP Professional SP3) Install CCleaner Free and leave settings as default
2. Open CCleaner > Options > Monitoring > Disable "Enable System Monitoring" and "Enable Active Monitoring"
3. Close CCleaner
4. Open command prompt and move to the installation directory.
5. Use - ccleaner.exe /auto
6. In the tray, I can see the CCleaner icon, the animated brush starts flashing, then the CCleaner logo leaves the tray.
[ I have also tested with the "Minimize to System Tray" enabled]
Could you please compare these steps to yours and let me know if there is anything different? Have you changed any of the cleaning settings from default? Added any Includes or Excludes?
A few people have posted on the forums since v4.18 was initially released about setting those to 0, so that CCleaner will not enable the tray icon.
Make sure you're using the newest version of CCleaner v4.18.4844 by downloading it from Piriform (to insure you actually have the newest version) which is supposed to fix the monitoring.
I experienced the exact same problem with CCleaner 4.18.4844; after cleaning with /AUTO the tray icon would stay visible and I had to manually exit the application.
As per instructions Heleny posted, I first enabled save settings to INI file and added all above mentioned entries to the bottom of my INI file, and auto close was suddenly working again. But because most settings were now double listed in my INI file, I started comparing them.
The only option that was not in my original file was: CheckTrialOffer=0
Edited the INI file to only leave this newly added setting, and auto close works! So this particular option seems to have been the problem for me.
Note: I had upgraded to the old 4.18 build, prior to upgrading to build 4844.