We cannot rely anymore on SSH authentication via "password" method to be generally allowed

I am trying to setup qt-creator for remote debugging on my beagleboard and raspberry pi. The raspberry runs the openssh daemon (openssh-6.1p1-2.1.armv5tel).

When I try to add a “generic linux device” in “Tools -> Options -> Devices” , the connection test always results in:

Connecting to host…
SSH connection failure: Server rejected password.

From the command line, I can ssh to the device without any problem, using the same username and password. I even tried to connect to another linux desktop i.s.o. the raspberry pi, which gives the same result: password rejected. I also tried it at work to rule out a network issue, same problem.

In the messages file of the targets I see this report:
2013-06-17T12:53:17.939553+00:00 raspberrypi sshd[7489]: Received disconnect from 10.6.11.147: 11: [preauth]

I left the “SSH port”, “Free ports”, “Timeout” fields all at their default value.

At last I installed dropbear next to openssh on the target (listening on different port). Then suddenly the connection from the tools->options->devices tab succeeds.

1) Why does the connection work only when the target runs dropbear iso openssh ?
2) If there is a good reason for this, then it should be clearly mentioned in the user interface and/or user manual.