Bug#746409: Problem solved.
I have not used the computer for several months. Then I discovered that the motherboard was broken. After replacing a new motherboard and updating Debian GNOME works correct.
dmesg|grep radeon output:
[ 5.511786] [drm] radeon kernel modesetting enabled.
[ 5.523032] radeon 0000:01:05.0: enabling device (0000 -> 0003)
[ 5.523333] radeon 0000:01:05.0: BAR 6: can't assign [??? 0x00000000 flags 0x0] (bogus alignment)
[ 5.523355] [drm:radeon_get_bios] *ERROR* Unable to locate a BIOS ROM
[ 5.523398] radeon 0000:01:05.0: Fatal error during GPU init
[ 5.523440] [drm] radeon: finishing device.
[ 5.524639] radeon: probe of 0000:01:05.0 failed with error -22
[ 5.526061] radeon 0000:02:00.0: VRAM: 512M 0x0000000000000000 - 0x000000001FFFFFFF (512M used)
[ 5.526064] radeon 0000:02:00.0: GTT: 512M 0x0000000020000000 - 0x000000003FFFFFFF
[ 5.526167] [drm] radeon: 512M of VRAM memory ready
[ 5.526169] [drm] radeon: 512M of GTT memory ready.
[ 5.579009] radeon 0000:02:00.0: firmware: direct-loading firmware radeon/RV730_pfp.bin
[ 5.586026] radeon 0000:02:00.0: firmware: direct-loading firmware radeon/RV730_me.bin
[ 5.588686] radeon 0000:02:00.0: firmware: direct-loading firmware radeon/R700_rlc.bin
[ 5.589641] radeon 0000:02:00.0: firmware: direct-loading firmware radeon/RV740_smc.bin
[ 5.605496] radeon 0000:02:00.0: firmware: direct-loading firmware radeon/RV710_uvd.bin
[ 5.608451] [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[ 5.622259] radeon 0000:02:00.0: WB enabled
[ 5.622268] radeon 0000:02:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and cpu addr 0xffb75c00
[ 5.622275] radeon 0000:02:00.0: fence driver on ring 3 use gpu addr 0x0000000020000c0c and cpu addr 0xffb75c0c
[ 5.625160] radeon 0000:02:00.0: fence driver on ring 5 use gpu addr 0x000000000005c598 and cpu addr 0xf8d1c598
[ 5.625216] radeon 0000:02:00.0: irq 44 for MSI/MSI-X
[ 5.625252] radeon 0000:02:00.0: radeon: using MSI.
[ 5.625303] [drm] radeon: irq initialized.
[ 6.043974] [drm] radeon: dpm initialized
[ 6.106284] fbcon: radeondrmfb (fb0) is primary device
[ 6.140265] radeon 0000:02:00.0: fb0: radeondrmfb frame buffer device
[ 6.140267] radeon 0000:02:00.0: registered panic notifier
[ 6.140273] [drm] Initialized radeon 2.36.0 20080528 for 0000:02:00.0 on minor 0
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