mysql_select_db in iframe dies

Hello all,
probably not a real wordpress issue, but i would be really happy if someone knows the answer to my problem.

I use a wordpress website and in one of the pages i load an iframe. So far so good… this works perfectly.

The only strange thing is that i cannot connect to my databse using “mysql_select_db”.

At this moment i even have added the username, password etc in the page that is loaded in the iframe. When i open the file directly in my browser it works perfectly. When i load the same page in an iframe… the db connection fails. (even with the login details hard coded in the file)

Anyone any idea? Is this some kind of safety issue? if so, can this be solved by overriding some sort of setting?

Best regards,
Herre