Unable to join server with Mojang/Minecraft account

[Sn0w]

I recently set up an MCDzienny server to play around with, setting up game modes, usual stuff.
All went well the first few times I ran it, friends were able to join using both ClassiCube accounts and Mojang accounts.
After some time I had issue when trying to set up a second server, I downloaded the software again but it never asked for an update when I ran it (I also ran the updater.exe countless times); I checked my firewall but nothing to see there.
I finally managed to get v11.0.0.0 from another computer and put it on my hostcomp. I now have the issue that only ClassiCube accounts are able to join the server. My first MCDzienny server is experiencing this issue too.
(Oh and if you are wondering why I didnt just duplicate the first server (which already was on v11, thats because it was setup as zombie and putting it to lava, which I wanted, gave me an error)
Did I miss out a configuration?

Thanks in advance.

[Sn0w]

Sorry, I didnt see the option to edit post.
Players from ClassiCube trying to connect now also disconnect, reason: Authentication failure.

[Leeizazombie]

Are you trying to host your second server on the same port as the first one? That might be the problem, then you would have to make a new port, also make sure you enabled "Verify Names"

[Sn0w]

No I am not trying to run the simultaniously on the same port (one is on 25565 and the other on 25566) both these ports are forwarded. Verify names is also checked.

[Leeizazombie]

You mentioned there was an error, can you post it?

[Sn0w]

I received this error trying to switch between zombies and lava survival on my first server.

Code: Select all

-------------------------
----1/12/2014 12:01:32 AM ----
Type: NullReferenceException
Source: MCDzienny_
Message: Object reference not set to an instance of an object.
Target: <PlayerLocationCheck>b__29
Trace:    at MCDzienny.Server.<PlayerLocationCheck>b__29(Player p)

-------------------------
----1/12/2014 12:52:56 AM ----
Type: ArgumentOutOfRangeException
Source: mscorlib
Message: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
Target: ThrowArgumentOutOfRangeException
Trace:    at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument, ExceptionResource resource)
   at System.ThrowHelper.ThrowArgumentOutOfRangeException()
   at System.Collections.Generic.List`1.get_Item(Int32 index)
   at MCDzienny.InfectionSystem.InfectionSystem.InfectionMapInitialization()
   at MCDzienny.Server.StartZombie()
   at MCDzienny.Server.<Start>b__c()


However I am able to join this server, though only with ClassiCube accounts.