Server Administration specific Configuration in TeamCity gets lost after refresh

I'd like to integrate NeoLoad tests into TeamCity. Therefore I've installed the corresponding NeoLoad Plugin and now I need to add a "NTS Configuration" to provide the mandatory license parameters for running the tests. The NTS Configuration has to be added at "Administration"->"Neotys Team Server".

I provide following required information: "URL", "Login User", "Login Password" and the label.

After saving it, the NTS Configuration is visible as a newly added entry BUT after switching to another page or after a refresh- the entry disappears. I've never experienced such a behaviour in TeamCity. I don't know whether it's about TeamCity or the NeoLoad Plugin.

I'm using "TeamCity Enterprise 10.0.5 build 42677" and NeoLoad 5.2.1.

Any guesses? Thank you a lot in advance!