Well if speed test are saying slower points to some sort of problem with conecvity it would appear.
But if IE is having issues (what version and is it updated fully?) worth looking if flash is up to date etc and what add ons etc you have. What version of Firefox do you have?
Have you checked flash module for IE up to date is your java up to date?
http://kb2.adobe.com/cps/155/tn_15507.html
Java?
http://javatester.org/version.html
Now Arthur will think im doing something saucy and offering Englishman some posh coffe