It seems like you have FURLs enabled in the other site (what produces links to be pageNN.html) and the FURLs are not working. So go to MODx manager and disable the friendly urls or fix the problem (eg. have you renamed the .ht_access file in MODx root folder to .htaccess and checked the RewriteBase etc. settings)...
"He can have a lollipop any time he wants to. That's what it means to be a programmer."