I've made a MASSIVE change to how the site works, as the server loads were crazy. I've still got one more change to make if this one doesn't do the trick, but I'll do that at the weekend late at night when not many people are online.
Please do let me know if you get any errors, as it would help me troubleshoot things
I think its to do with the version of PHP, IIS, MySQL and other bits of software not working together properly. I've tried lots of combinations and this was the most stable at the time, but it's due a bit of an upgrade I think.