The new Yahoo! uses lots of AJAX. What solved that problem for me was uninstalling JAVA totally. I didn't realize it but I had like ten updates in there. Fresh install of JAVA, no more problems.
Hope it works, did the trick for me.
But if you really want to fly on Yahoo!, use Firefox with the adblock plus plugin. Them video ads take alot of time to load.
After you do that add http://*.googlesyndication.com/* to your filters and you're flyin.
Have Fun! Dan