After the "Trojan Nyetya" was found in Ccleaner installer 533 in my downloads file by Malwarebytes and quarantined. I noticed my Ccleaner version had reverted to 5.28.6005
Try uninstalling CCleaner while in Safe Mode then restart the computer, Do a scan with Malwarebytes and once no errors - download a fresh copy of the 534 inastaller and see if that he;ps you?
First make sure ccleaner including monitoring (system tray) is exited, that's the usual cause of this. If still can't install, go to http://www.piriform.com/ccleaner/builds
download the portable build
copy ccleaner.exe and ccleaner64.exe, found in zip, to your c:\program files\ccleaner folder. You'll need administrator's privileges to do this depending on your pc's UAC settings