If the pages are loading slow because they're trying to read cookies that are corrupt, clearing cookies will eliminate the problem.
Might try cleaning out your cookies.
What possible effect would that have?
But if they're trying to load non-corrupt cookies that aren't there, and the site was written by some wiz-kid who's been in the business a whole 3 weeks, it could bring the browser to its knees.
Delete individual corrupt cookies (they're text files so, aside from encrypted data, they're human readable), but don't delete all cookies wholesale. (For one thing, all sites you log into, or saved data on - like shipping address, preferences, etc. - will "forget" the data you saved.)
As far as ccleaner causing problems, there was a problen 3 months ago, so the person installed ccleaner 2-1/2 months ago and the computer needs repair. Could be that ccleaner can't fix that kind of problem, and it just kept compounding. I have computers that ccleaner has been running on for years - and it never caused a problem. (It fixed a few, though, more easily than if I had fixed them manually.) Should everyone run it? Of course not. Probably 50% of the programs being run today should only be run by computer experts. Try telling that to people who can't find the "any" key.