I have a similar card (also the xpress 200m), I will try to reproduce this bug. However, Rodrigo's Xorg0.log shows all these warnings and errors.
(WW) RADEON(0): Direct rendering disabled (II) RADEON(0): XAA Render acceleration unsupported on Radeon 9500/9700 and newer. Please use EXA instead. (II) RADEON(0): Render acceleration disabled [355167.718141] [drm] Loading R300 Microcode [355167.818662] [drm:radeon_do_init_cp] *ERROR* Failed to load firmware! Perhaps these need to be addressed to fix your other issue. Please install libdrm-radeon1, firmaware-linux, firmware-linux-nonfree. Also use EXA in your xorg.conf For example: Section "ServerLayout" Identifier "Default Layout" Screen "Default Screen" EndSection Section "Device" Identifier "ATI Radeon Xpress 200M" Driver "radeon" BusID "PCI:1:5:0" Option "AccelMethod" "EXA" Option "AccelDFS" "1" Option "EnablePageFlip" "1" Option "Monitor-LVDS" "Internal Monitor" EndSection Section "Monitor" Identifier "Internal Monitor" EndSection Section "Screen" Identifier "Default Screen" Device "ATI Radeon Xpress 200M" Monitor "Internal Monitor" DefaultDepth 24 SubSection "Display" Depth 24 Virtual 2560 1824 EndSubSection EndSection Please report back! Andres