problem logging in, now

[David]

Hope i'm sending this to the right place!

All of a sudden, I can't login anymore.  Running Jessie on AMD64 desktop 
and everything is up to date.
However, I did just install an R9 280X video card, but I'm pretty sure I 
logged in a few times before this error showed up.
Upon system boot, I get the gui and the login prompt.  But, when  I 
login as myself OR root, it changes to an all-white screen and says 
something about login problem.  When I ack the problem, it falls back to 
the initial screen but with no text or icons on it and no way to 
interact at all.

At this point, I can move into the text shells and do stuff via command 
line, but everything I do now is via the gui, even email.

Here is the contents of ".xsession-errors":

Xsession: X session started for david at Sun Mar 27 01:13:40 CDT 2016
localuser:david being added to access control list
openConnection: connect: No such file or directory
cannot connect to brltty at :0
Xlib:  extension "GLX" missing on display ":0".
Xlib:  extension "GLX" missing on display ":0".
Xlib:  extension "GLX" missing on display ":0".
gnome-session-is-accelerated: No hardware 3D support.
Xlib:  extension "GLX" missing on display ":0".
gnome-session-check-accelerated: Helper exited with code 256
Xlib:  extension "GLX" missing on display ":0".
Xlib:  extension "GLX" missing on display ":0".
Xlib:  extension "GLX" missing on display ":0".
gnome-session-is-accelerated: No hardware 3D support.
Xlib:  extension "GLX" missing on display ":0".
gnome-session-check-accelerated: Helper exited with code 256

** (process:1991): WARNING **: software acceleration check failed: Child 
process exited with code 1


Can you guys help me get my computer back?  Others around the web have 
had the same problems and are calling it a bug.

Thanks,
David
<this email is coming from a different computer>