@Mikeh, I experienced these problems from day one I installed DNN 4.3.5. So, it has definitly nothing to do with the 'AD fix'. The problems already existed before the fix.

@Stuart, I have checked all the settings you are describing and I found two differences. One thing I did extra was removing the 'anonymous' permissions from the whole website and not only the "WindowsSignin.aspx". Then I created a new domain group so I can control the access to my website via IIS security (actually NTFS security). The website is not supposed to be available for everyone. The other thing is that I also commented out the "authentication=Forms" and enabled "authentication=Windows" in web.config. Does this mean you actually work in mixed mode?

I think I've read must of the threads about these issues the last two weeks. In the beginning I thought it was related to the 4.3.5 release as multiple people having the same problem. But when I saw the messages in this thread I noticed that people actually have Windows Authentication working with 4.3.5.

Nevertheless, I think its the savest way to just do a clean install with DNN 4.3.5 using your manual. It shouldn't take to much time to do this. I'll let you know when its setup to see if there are any improvements. Thanks again, guys! I really appreciate this.

Kind regards,
Dennis

I will do that.

Stuart

Well, reading the 4.3.5 instructions it appeared to be almost ridiculousy easy to implement, so I did it sooner than planned. 

So far, so good.  Logins "appear" to be faster, but I can't tell for sure.  The display name no longer shows "first name, last name", now it displays the "display name" entered into AD, which is the inverse of that. 

The biggest thing I've noticed so far is the lack of error messages in the system.  Quit often, during the peak usage times (a good hundred mad clickers working in unison), I'd get a series of two error messages in the logs.  The first one a "The RPC server is too busy to complete this operation." error, followed immediately by a "Object reference not set to an instance of an object." error.  So far, I have not gotten any errors at all since implementing the fix!  This is quite an improvement, as the webserver is on an awfully fast box, I couldn't figure out why it was getting busy errors.