OK. During posting I think I found the reason for this behaviour.
I have 1 Dimension and 2 Expressions.
1. Expression = sum(somevalues)/60
"Display Options" --> Bar, Values on Data Points""
2. Expression = [One Field] --> contains labels to draw in the chart, additional to the dimension labels.
"Display Options" --> Values on Data Points"
Nothing special at all...
If I untick the box for "Values on Data Points" for Expression No.1 no error msg appears anymore. I assume it's the same vice versa.
I'm quite sure the activation of "Values on Data Points" in both expressions leads to the described error.
Message was edited by: peschu82 Reason: Typo