Reason: the URL contains a parameter with the pool name - and the 2nd user is not mapped to that pool.
I think that it doesnt happen when the portal is not opened from Studio.
This is not a big deal, I just think it could confuse the user (or even the developer) before one understands whats going on.
Maybe the logout function can redirect to a simple, basic URL, no params, as it happens when portal is used outside Studio.
windows 7, firefox, Bonita Studio 6.03
The message is a warning only - the user is logged in.
To go forward from there, just click on the PORTAL link on the top right.