Looking at neuromancer Xorg log, I found out:
[     7.278] (--) RADEON(0): Chipset: "SUMO" (ChipID = 0x9641)
[     7.548] (--) RADEON(G0): Chipset: "TURKS" (ChipID = 0x6741)

I think its a problem only with two devices with radeon driver...
After closing client, the destroy buffer is called twice, and causes the
error...

I can workaround, but I cant fix it the right way... I have no experience with
Xorg or radeon driver... I dont know either how to edit the subject of the
bug...

Please... Help us...

Thanks in advance!
Weber Kai