I can confirm that CCleaner v1.37.456 is working fine with x64 Vista Ultimate.
I have a problem Vista Ultimate 64-bit. I can't delete 31 problems (ranging from "default icon is invalid" to "activeX/COM problem"). CCleaner keeps on prompting them...
sorry if translations of problem are not 100% accurate but I'm using the Italian version of CCleaner.
On the 32-bit Vista Ultimate, CCleaner is unable to delete the Internet Explorer's browsing history, and I don't know, whatelse!