I have been running BOClean for a couple of weeks. One day last week, after logging in, the BOClean icon was green and Task Manager showed that a BOClean process was taking 99% CPU. After 20 minutes of this, I rebooted the PC, and BOClean returned to normal.
This is my PC at work. My PC is behind a password-protected proxy, and BOClean does not seem to grab the proxy info from IE, so auto updates does not work, and I have it disabled.
The BOClean icon turns blue while it scans after login, and this usually takes less than a minute on my PC. My PC runs at 3GHz and has 1GB RAM, so it is pretty zippy. My PC runs McAfee AV and no local firewall. I brought up MS Outlook right after login. I was reading emails for about 20 minutes, noticing how slow my PC was, when I investigated and found out the problem was BOClean. I shut down Outlook, and BOClean continued for several minutes to use 99% and keep its icon green. Then I gave up and reboot.
Hope this enough info to help find a bug within BOClean.
Edit: My PC runs Windows XP Pro SP2