Transaction iViews default to SAP-GUI Windows

Hi,

System Information: ECC 6.0 EHP 4 SP 46 Stack 10. Portal Netweaver 7.01 SP 11 (Our basis guys said, it wouldn't be a problem if Portal Stack is higher than Backend 😕).

First of all, what makes this issue particulary deceptive is, that it is somehow related to permissions in Backend. Whenever I open transaction iViews (property configured as "SAP-GUI for HTML") with users that have certain permissions (up until know I've observed SAP_ALL and the default Developer Role), it works just fine.

However, if I try to open these iViews with a user that has neither Role/Profile, a download prompt from Inet Explorer opens up and defaults to SAP-GUI for Windows which inevitably fails:

I tried to track this down using ST01 because I wagered there has to be SOMETHING, at least a security check or a database query, but the ST01 Trace is completely empty... the NWA tracelog shows nothing either, except "LOGIN OK!" -.- so I'm really stuck here. Does anybody have an idea? I fear for the worst (probably it's due to stack missmatch). Has somebody ever experienced something alike?

Please help ;-/

Cheers, Lukas