This is not really a ccleaner issue. I have notified postbox support. I have tested and with postbox client open ccleaner hangs at 1 percent complete. It will hang for hours if you let it. When you close postbox, ccleaner completes cleaning
The latest version of CCleaner (downloaded yesterday) 3.12.1572 (64bit) complains that Firefox must be closed to clean cache. Firefox is closed and the process is not running. This did not occur with the previous version
Windows 7 64bit