You need at least Internet Explorer 10, or you may want to give Firefox or Chrome a try.
flash support in newer browsers gets more and more bad
EDIT: sometimes older versions provide better flash performance.
e.g. firefox 4.0 provides a significant better flash performance then the latest version, firefox 14.1
try it out, you can find old versions of firefox here:
(need at least version 4.0, on older versions the latest flash plugin won't work)