LightDM Login Prompt Dropdown Default

[Gilbert Sullivan]

Hi.

I'm your friendly neighborhood moron. I accidentally sent the following 
e-mail from my unsubscribed e-mail account with Comcast. Now I'm 
re-sending to the list from the correct account. (But I'm probably 
asking my question on the wrong list anyway. If so, please feel free to 
ignore me or flame me, as you deem is deserved.)

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Hi.

I'm using LightDM with Xfce 4.8 in Debian testing (fully updated).

On my systems when an end user simply enters user name, hits <Enter>, 
enters password, hits <Enter> s/he gets a popup that says:

Xsession: unable to launch "(null)" X session --- "(null)" not found; 
falling back to default session.
okay

The user then has to fiddle around with the mouse for a while before an 
"X" cursor will appear so that s/he can click on the okay button. 
(Hitting <Enter> doesn't "press" the button.)

The dropdown defaults to Default Xsession instead of Xfce Session. If 
Xfce Session is chosen, then the login proceeds without the popup.

Intended behavior?

I've examined and tested changes in the files located in /etc/lightdm 
and /usr/share/xsessions but haven't had the effect I'm looking for. Is 
there documentation for end users?

Thanks,
Gilbert

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