[SOLVED] ADFS - Invalid URI: The format of the URI could not be determined

I have created a test website that I want to login to using an ADFS server connected to a AD. When I use the generated STS-provider project the loing works fine but when I try to use a real ADFS server installed on a win 2008 server I get this error message:

[UriFormatException: Invalid URI: The format of the URI could not be determined.]
   System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind) +7225919
   System.Web.Security.SingleSignOn.SignInResponse.get_Target() +164

[InvalidOperationException: The protocol message in the current request is malformed. The event log on the server contains detailed information.]
   System.Web.Security.SingleSignOn.SignInResponse.get_Target() +488
   System.Web.Security.SingleSignOn.LSAuthenticationObject.RejectBadMessagesPhase1() +643
   System.Web.Security.SingleSignOn.LSAuthenticationObject.EnsureCurrent(HttpContext context) +445
   System.Web.Security.SingleSignOn.LSAuthenticationModule.OnEnter(Object o, EventArgs args) +147
           System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +171

When I access my website I get redirected to the ADFS server and prompted for credentials. So far so good. But after I supply the correct credentials it seems that it fails when it tries to create the response ticket?

Does anyone got any ideas what I have done wrong or what URI the error message might refer to?

---- Update with more logs and error messages ----

There are two eventlog entries, none of them gives much help:

A sign-in message was received that contains incorrectly formatted data. 
Format error: Invalid URI: The format of the URI could not be determined. 

This situation can be due to rogue clients; interoperability failure with non-Microsoft, single-sign-on software; or message tampering. 

User Action 
If you are using non-Microsoft federation software in your environment, verify that the federation software is compatible with AD FS.

And

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 2013-10-01 14:48:09 
Event time (UTC): 2013-10-01 12:48:09 
Event ID: aa19d901b4af49009aaa65310b7ccf22 
Event sequence: 33 
Event occurrence: 6 
Event detail code: 0 

Application information: 
    Application domain: /LM/W3SVC/1/ROOT/adfs-2-130250981254471250 
    Trust level: Full 
    Application Virtual Path: /adfs 
    Application Path: C:\Windows\SystemData\ADFS\sts\ 
    Machine name: WIN-U9HD61HVTHM 

Process information: 
    Process ID: 1344 
    Process name: w3wp.exe 
    Account name: NT AUTHORITY\NETWORK SERVICE 

Exception information: 
    Exception type: UriFormatException 
    Exception message: Invalid URI: The format of the URI could not be determined. 

Request information: 
    Request URL: https://10.100.13.67:443/adfs/ls/clientlogon.aspx 
    Request path: /adfs/ls/clientlogon.aspx 
    User host address: 10.100.13.91 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: NT AUTHORITY\NETWORK SERVICE 

Thread information: 
    Thread ID: 3 
    Thread account name: NT AUTHORITY\NETWORK SERVICE 
    Is impersonating: False 
    Stack trace:    at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind)
   at System.Web.Security.SingleSignOn.SignInResponse.get_Target()


Custom event details:

I also enabled all the logging I could find and in the log the sign in response seems to be:

[VERBOSE] Sign In Response Dump
--------------------
wcontext = rm=0&id=passive&ru=%2fdefault.aspx%3f
wresult to follow
XML Data Follows
----------------
<wst:RequestSecurityTokenResponse xmlns:wst="http://schemas.xmlsoap.org/ws/2005/02/trust">
  <wst:RequestedSecurityToken>
    <saml:Assertion AssertionID="_c7434b4c-88d6-4648-974d-cf0dc1582958" IssueInstant="2013-10-01T12:49:05Z" Issuer="https://WIN-U9HD61HVTHM.adtest.local/adfs/" MajorVersion="1" MinorVersion="1" xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion">
      <saml:Conditions NotBefore="2013-10-01T12:49:05Z" NotOnOrAfter="2013-10-01T13:49:05Z">
        <saml:AudienceRestrictionCondition>
          <saml:Audience>https://10.100.13.67/adfs/</saml:Audience>
        </saml:AudienceRestrictionCondition>
      </saml:Conditions>
      <saml:AuthenticationStatement AuthenticationInstant="2013-10-01T12:49:05Z" AuthenticationMethod="urn:federation:authentication:windows">
        <saml:Subject>
          <saml:NameIdentifier Format="http://schemas.xmlsoap.org/claims/UPN">per@adtest.local</saml:NameIdentifier>
        </saml:Subject>
      </saml:AuthenticationStatement>
      <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
        <SignedInfo>
          <CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
          <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
          <Reference URI="#_c7434b4c-88d6-4648-974d-cf0dc1582958">
            <Transforms>
              <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature" />
              <Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
            </Transforms>
            <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
            <DigestValue>3VkZjrL3Lyej2UhVJtiSvL1K7u4=</DigestValue>
          </Reference>
        </SignedInfo>
        <SignatureValue>PEYPQ4FSOvf2LCH1UEPUD9TTd9M7jZT8isw578G7TVgk01HecoaH1p7KCTpcnGpG+aQlmtR6D1oyXYKwwsij9aLVeWT/zxqf1PjxfAfQL19t6KZMwZJOhV2XCfdqfsgEbFHIUU/4KGstwghCHLGMTVUXVx2p2FAs0VO1AV42Ua3M+ZMpx2rWWeEdh9OGMSysFug+D2gFMytcwlbVLBaPMbs8mNfXGm84CWMJ9ctM4XbwkBhfPnhvKyYcNeu1dic13ky4Rb6ODRejZhfwKXr8g2fSkV2QrnZLo8VNBBUD2+tVB/fCIThIiyrHfD7Rou8yChePHKYoYnhY6jmlBUJSrQ==</SignatureValue>
        <KeyInfo>
          <X509Data>
            <X509Certificate>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</X509Certificate>
          </X509Data>
        </KeyInfo>
      </Signature>
    </saml:Assertion>
  </wst:RequestedSecurityToken>
  <wsp:AppliesTo xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy">
    <wsa:EndpointReference xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
      <wsa:Address>https://10.100.13.67/adfs/</wsa:Address>
    </wsa:EndpointReference>
  </wsp:AppliesTo>
</wst:RequestSecurityTokenResponse>