Layout changes with user registration

When putting a "Log In" in the main menu and subsequently choosing "Register New" the layout changes and below the registration module a new instance of the header with menu appears. Would you know how this can be fixed?

Same thing happens when adding a search function to module position "top 2".
The search results generat the whole page again underneath the module.

Pls check on www.targettraining.se

How could I test that? If you need to send me username/password use 'report to moderator'

Oh, sorry I missed that.
You can go to the site, press "logga in" in the menu and then one of the three options below the log in button and you'll see how it looks like.

It looks ok to me , what browser do you use ?

Latest version of Firefox (32.0.1)