Search Filter Invalid

I have seen a few questions pop up here in regards to this message:

<form id="form1" method="post" action="./Error.aspx"> <div>Message: The (&(objectClass=user)(objectCategory=person)(sAMAccountName=)) search filter is invalid.

I have tried all the suggestions, adding in 

<authorization><deny users="?" /></authorization>

and

<system.webServer><validation validateIntegratedModeConfiguration="false" /></system.webServer>

to the web config. I have also installed windows authentication to IIS as suggested on a post too. That denies my windows credentials though as unauthorized on the server (but in local host through VS, this all works). Is there a security feature I am not setting up or something missing in IIS?