"Returned Fault: NetConnection.Call.BadVersion" at entering a model number

[Mike14]

Hi,
after using the software for more than a year without trouble, I just tried to add a new article. I get this error when I try to edit the model number. All other fields look correct.

I tried to update the software but I already was up to date.
I tried to use the admin console on the server and not local - same problem.

[Mike14]

I found it working very slow in firefox but working, fast in chrome but with errors. mhm...