I don't remember this happening yesterday, but once I've started browsing with IE8 today I quickly discovered that I wasn't able to open links in a new tab or window. Selecting open in new tab from the right-click context menu when clicking on a link caused a new tab to open with the title 'Connecting...', in the right tab color (tab grouping feature), but there was no address in the URL bar and the page never loaded while the open Link in New Window wasn't doing anything at all.
What's more I noticed that Windows Explorer (not IE) was always opening new folders in new windows even though I've had specifically set it to open new folders in the same explorer window.
Arghhh.... after running a few tests, running the browser in no add-on mode, and disabling features one by one I've discovered that both problems go away by turning IE8 quick tabs off.
Bug submitted here. Please rate it so that it gets fixed.