Hi Tom,
I can assure you the shoutbox is not "infecting" anything, there is no malicious code in it whatsoever. As the person doing the coding work on this site, I find it a bit distressing when people throw around terms like this without understanding what they mean. It's enough to freak out more casual users, and just obscures the real issue.
The shoutbox does work by refreshing the content of the iframe it's in every couple minutes, this is how you get to see shouts that are made while you're on the site. The entire page shouldn't be refreshing, just the shoutbox itself.
If you're having problems after closing the tab you were on booktalk in, or after navigating away from the site, then there is definitely something wrong with your browser, or possibly with additional software you've installed on it.
I strongly suspect this is an IE issue. Can you please get us the version of IE you're using? You can do this by clicking Help then About on the menu bar near the top.
Could you also list any plugins or additional software you've installed on IE, and tell us what security software (antivirus and firewall, or "internet security" suite) you're using?
In the meantime, if you're using IE6 and need to disable the shoutbox from refreshing at all you could try this:
1. Click Tools in the IE menubar near the top, then click Internet Options
2. On the Security tab click Custom Level.
3. Scroll down to where you see "Allow META REFRESH" and change "enable" to "disable".
4. See if that solves your problem.
If you're using IE7 or IE8 then the process may be a bit different. Post back and let us know.
If you want some friendly advice, ditch IE and get Firefox. Not just because of this issue, but because it's a better, safer browser.