I just tried the add-on Ted Talks V4.2.0 on Gotham seems to work well. Tried Ted Talks V4.1.9 on Frodo and found a script failure, updated the add-on with V4.2.1 (your version) and still a failure, it looks like Ted Talks is caught between iterations and suspect it's not something you did. But at least you can see that add-ons and support are flighty and patience is required. I suspect that a new version will be around soon.
Entry of setups>addons>Get addons>hover over xbmc.org addons.org and hit keyboard 'c' will check for updates or force refresh of the add-ons.
On another note: a re-install of XBMC for most is just clicking on the installer, but rarely does this clean malformed code. Going into C:\Program Files (x86) and C:\Users\PatK\AppData\Roaming\XBMC for a rename or delete does give you a fresh slate. In the case of these add-ons, some have not been extensively tested and rely on user reports and co-operation of the community in general to debug and make the add-on stronger. The Ted Talks forums is
http://forum.xbmc.org/showthread.php?tid=36866 and the wiki here
http://wiki.xbmc.org/index.php?title=Add-on:TED_Talks your input would be appreciated.
A better plugin to work on would be Youtube, it's been relatively flawless on my end.