Hi Frank,
Thanks for your help.
Yes, UI_INFRA 100 SP3 and UI5_731 100 SP3 are installed.
The note 1684342, mentioned in the guide, should be obsolete as we are on a higher SP level.
Still unsure what might e the problem.
I thought it might be the SAP Gui as it is rather old (7.2 SP 10), but ABAP integration works fine, so I assume it's something else.
Regards
Andre