OK, I had a problem yesterday. I had done an upgrade from Debian Stable to Debian Testing/Unstable. I had done backups, as usual, and did a recovery from my $HOME and /root. (1/2 of my drives are backups (I have been bitten in the past))

I had installed the most recent version of the Proprietary Nvidia Driver ((version NVIDIA-Linux-x86_64-384.90}}

I had all kinds of trouble trying to get steam to work:
"libGL error: No matching fbConfigs or visuals found"
"libGL error: failed to load driver: swrast"
"X Error of failed request: BadValue (integer parameter out of range for operation)"
"libGL error: No matching fbConfigs or visuals found"
"steamupdateui: An X Error occurred"
AND OTHER SUCH CRAP!!!

I purged Steam, deleted my ~/.steam directory, did a reboot, reinstalled steam to no avail.

Then I uninstalled the current Nvidia driver, did a reboot, installed the previous version {{version NVIDIA-Linux-x86_64-384.69}}, did a reboot, ... and IT worked.

{sigh} it has been a hell of a day.

Anyway, that was my solution to this problem.

Good job, posted mostly to get this off zero reply list.