Problems with content.php / Articles

[horseguards]

Hello,

I am relaunching an old and almost abandoned forum, so I upgraded it to vB Suite 4.2.2.

I bought a new theme http://themeforest.net/item/primus-a...-suite/3321272, and so far so good.

Now, I am having a problem with the "tab" Articles.

In the default theme it works OK, but with the new theme, the links goes to xxx.com/content.php (I see it when I put the mouse over), but when I click, it takes me to
xxx.com/cms/content/ and shows this

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Not Found

The requested URL /cms/content/ was not found on this server.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.
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Can anyone give me an idea of what could be going on?

Thanks in advance.