Hi Klaus,
I would try re-deploying all the .resx files in case something got corrupted.
"App_GlobalResources.rnhct_hz" isn't a name of one of our resource files so it seems to be referring to something that the ASP.NET compiler generated down under C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files
Redeploying the .resx files may make it re-generate those temp files and that may solve it.
I have seen times when things get really funky in those temp files. You can safely delete them and they will be re-generated but it may require stopping the web site or stopping IIS because you can't delete files that are in use.
Hope that helps,
Joe