There are some things that worked for people who had the same problem here. http://webtrickz.com/how-to-fix-open-in-ne...problem-in-ie8/
Open in new tab is not missing in IE8 ,you simply have not enabled it. To enable it ,open Internet Options, Beside Tabs,click Settings, where it says "When a new tab is opened ,open", in the drop down menu choose "the new tab page".Click OK. Now close IE8 and relaunch it. TA DA! You now have "open in new tab" in your right menu.