I have IE 8 on Vista. IE constantly closes because of some security attack. How can I fix this? Thanks.?

Since changing over to new ATT Yahoo, my browser is constantly closing down. This happens every time I read my email messages. This is also happening when I am not in my mail. I am not feeling secure when I log onto the internet any more. I am on Vista 64 bit. I have had McAfee security software for a few years. Is ther a fix for Internet Explorer? Should I change back to IE 7? I have checked my DEP settings. Everything is OK except for this security problem with IE. Thanks for any help you can provide. Donna