For the past few weeks I've been getting "Curse Client v4 could not establish a connection with the update server". Basically renders Curse nonfunctional. It only seems to affect Curse, which I've been using for years with no problems. Anyone else having these issues?
Which version of IE? If you can connect via one browser but not another, it is typically a browser issue. You need to try wiping out the cookies for that browser (especially any and all Curse cookies). You should also try a DNS flush. One version of IE often has issues with the Curse site.