Ever since IE 7 was released, I've seen this issue sporatically, and now its happening to my machine. Basically, the run once page that loads will come up with an error on page in the bottom left bar on of Internet Explorer, that says "Error on Page". When I try to add a search provider to IE, it also gives the same error and also says at the top of the page "Settings were not able to be saved successfully".
If you double click the error, it says "Problems with the web page might prevent it from being displayed properly or functioning properly. In details it says the error is line 80, char 5, Error: Element not found, code: 0, URL: http://runonce.msn.com/runonce3.aspx
Thanks for any help!!