When I view the page source I can see that the last thing to occur is this td:
<td width="100px" align="left" class="text_mediumIndex_01">
This occurs just after the login link. What is the php code that you have on this line in your page?
Also what is the complete error message you are getting? When you see a fatal call to member it is usually referring to a particular function that is on the page that has not been defined. If the function is custom then you may be missing a necessary include file that defines that function. If it is a built in PHP function then your php server may not be configured with support for the module that the function comes from.