TaminoClient often throws TaminoError with responseCode 8400

What does this mean? The problem often, not always, occurs when reading a single Element which is bigger than 87KB.

The code is:

TaminoClient tamino = new TaminoClient(/Col);
TaminoResult tr = tamino.query(Xpath);
if ( null == tr) {
System.out.println( “result is null”);
return tr.getResult();
} catch (TaminoError e) {
System.out.println("Err.Text " +e.errorText);
System.out.println("Resp.Code " + e.responseCode);
return null;

The result is:
Err.Text HTTP error -1
Resp.Code 8400
result is null

Has anyone any idea what is going on? And what can I do to resolve the problem?