If you are using mod_rewrite on apache, or similar on other web servers, you should check the configuration.
It looks as if the web server makes the request /x/ turn into /x.php
If wordpress works with the “good looking”-urls, a solution would be to name the pages on wordpress slightly different from your original ones. Like /page-1/ -> /page1/ to work around it.
While I’m not into wordpress at all, I could imagine that they use the same kind of rewriting as I do.
– check if requested file exists – e.g /css/stylesheet.css
– if it does – return that file
– otherwise – return some-bootstrap-file.php?url=…
So, if your wordpress page is named the exact same as your old page, this would screw it up and be the cause of the infinite loop – and thus – our little workaround would work…