Re: SERIOUS bugs - customers being logged in as other customers, super slow, etc. HEL
Neither of those is a bug-
You or your customers have posted URLs with an active session ID somewhere and when that gets clicked they see the ssession of the other person.
Solw is your host - do a search for dreamhost.
Please do not PM for support issues: a private solution doesn't benefit the community.
Be careful with unsolicited advice via email or PM - Make sure the person you are talking to is a reliable source.