stop 404 if ? or & in URL

[eluser]faceh[/eluser]
I have recently updated an old version of an eCommerce website which previously relied on query strings such as index.php?page=thispage&options=theseoptions&etc;...

Now I use the codeigniter friendly urls /like/this/instead

However, a lot of search engine results and external links still point to the old URLs. Currently, Codeigniter just dies and says "The URI you submitted has disallowed characters." or gives a 404 Page not found.

I want to catch all of these requests and send them to my new pages. I have tried using routing, but it seems when there is a disallowed character it doesnt even get as far as the routing class.

Any Ideas?