Have you ran any of your anti-malware security program.
I/E8 is running very slow at the moment on the PCA Site.
So you are not the only one having problems.
Firefox is not much better just now either.
You have not got a different Host file downloaded have you.
i used to have this one.link text
I was having the same problem as yourself and after trying just about everything I removed the Host file, and everything is fast on IE8 now.