Error with "poker" in the URL


Today an user has registered a blog in my site called “poker”. Then the address was, but this address don´t charge the css, and gives error at enter the control panel.

I have tried many variations e.g. (“blogdepoker”, “miblogdepoker”, “pruebaspoker”:wink:, but if exists the word poker it crashes.

I tested also with poker word variations e.g.(“oker”, “roker”, “poko”:wink:, and this works fine.

It´s a WordPress bug?