Is it possible that someone with ill intent that requested a Temp host account could have caused this? I had a problem with a 3rd party module awhile back and asked about it on their forum, they did access the site but have never made a comment about the issue on their forum (I have since dumped their module and two others I had to buy to make the whole thing work). And I notice that others are asking if the their site is active as they too are not getting any response from them.

I could be clutching at straws here but I think that this issue began after they accessed the Host account.

Famous last words. Was fixed for 4 days and this behavior has started again.

Just logged on as Admin and can navigate to any Admin page but go to a general user page and I'm not logged on. Does anyone have an idea what's going on here?

Just tried this. Logged on with Host account, different browser and the same thing happened. Can navigate Host and Admin pages, go to a "All Users" page and I'm logged out. Return to previous page and I'm still logged on.