I've got it sending an "X-XRDS-Location" header pointing to my Yadis document, and I've also included link entries in the head portion of the HTML. For some reason, however, I still can't use "pkulak.com" to log in anywhere. Thanks for any help!
I got OpenID working on my domain (powered by Wordpress as well) by following the instructions in this blog post: http://simonwillison.net/2006/Dec/19/openid/.
When I tried entering "pkulak.com" into the test OpenID RP at http://nerdbank.org/rp.exp/login.aspx, I got a 404 error. You can try it out yourself and then look at the http://nerdbank.org/rp.exp/tracepage.aspx URL to see the logs of what the RP ran into while trying to "discover" your OpenID.
Since a browser has no problem avoiding this 404, I suspect your web server is configured to reject HTTP requests that lack certain HTTP headers that are common to browsers. For example, some RPs don't send a user-agent HTTP header and some web servers reject requests that lack this header. I suggest you start your investigation there.