Explorer 8 behaving strangely, anybody else experiencing this or is it a Trojan

Hi, I’m having a lot of problems with explorer 8 out of nowhere. I don’t visit any dodgy sites, just youtube, ebay and some other safe sites so I don’t think I’ve been infected with a virus. I was infected with a Trojan once and that reduced the security setting in explorer but that hasn’t happened this time. The computer is new only a couple of months old with Windows 7 and explorer 8, I’ve tried to go back with system restore but restore failed. The problem is that when I open multiple tabs, the new tab will freeze, sometimes immediately and other times after a minute or so. Trying to close them doesn’t work, and that causes to first tab to freeze and I have to right click and close. After this happens, I can’t access internet options through explorer after restarting it, I have to access the options through the control panel and delete the browsing history before I can access options through explorer. I checked the restore points and the first was today for a critical update, that worked but there was no change with the problem, next restore point was 5 days ago and that failed due to an unspecified error (I think that’s what it said). Could the critical update cause this or is it more sinister?