I'm assuming you upgraded to the crappy Internet Explorer 7 no doubt.
Reset tab settings if you did.
Click TOOLS» select Internet Options
The Internet Options dialog box appears.
Select the General tab
In the Tabs section, click SETTINGS
The Tabbed Browsing Settings dialog box appears.
Make the desired settings changes
OPTIONAL: To restore default tab settings, click RESTORE DEFAULTS
To save changes and close, click OK
To cancel changes and close, click CANCEL
To close the Internet Options dialog box, click OK