Dual Envision monitors on a Radeon 8500 yields:

[   16.072653] i2c i2c-0: sendbytes: NAK bailout.
[   16.072718] [drm:radeon_vga_detect] *ERROR* VGA-1: probed a monitor but no|invalid EDID
[   16.075223] i2c i2c-0: sendbytes: NAK bailout.
[   16.287729] i2c i2c-0: sendbytes: NAK bailout.
[   16.287793] [drm:radeon_vga_detect] *ERROR* VGA-1: probed a monitor but no|invalid EDID
[   16.288597] i2c i2c-0: sendbytes: NAK bailout.


...with useless resolutions, depths, and frame rates for my work, thus I have to leave 10.04 LTS and go BACK to 9.x where I spent enough time to get it working fine.

Info:

P: /devices/pci0000:00/0000:00:01.0/0000:01:00.0
E: UDEV_LOG=3
E: DEVPATH=/devices/pci0000:00/0000:00:01.0/0000:01:00.0
E: DRIVER=radeon
E: PCI_CLASS=30000
E: PCI_ID=1002:4150
E: PCI_SUBSYS_ID=1002:4722
E: PCI_SLOT_NAME=0000:01:00.0
E: MODALIAS=pci:v00001002d00004150sv00001002sd00004722bc03sc00i00
E: SUBSYSTEM=pci


[   12.941549] [drm] radeon defaulting to kernel modesetting.
[   12.941556] [drm] radeon kernel modesetting enabled.
[   12.941634] radeon 0000:01:00.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
[   12.946488] [drm] radeon: Initializing kernel modesetting.
[   12.953154] [drm] register mmio base: 0xF9000000
[   12.953159] [drm] register mmio size: 65536
[   12.955276] [drm] GPU reset succeed (RBBM_STATUS=0x00000140)
[   12.955302] [drm] Generation 2 PCI interface, using max accessible memory
[   12.955316] agpgart-intel 0000:00:00.0: AGP 3.0 bridge
[   12.955343] agpgart-intel 0000:00:00.0: putting AGP V3 device into 8x mode
[   12.955395] radeon 0000:01:00.0: putting AGP V3 device into 8x mode
[   12.955422] [drm] radeon: VRAM 128M
[   12.955426] [drm] radeon: VRAM from 0x00000000 to 0x07FFFFFF
[   12.955430] [drm] radeon: GTT 128M
[   12.955434] [drm] radeon: GTT from 0xE0000000 to 0xE7FFFFFF
[   12.955464] [drm] radeon: irq initialized.
[   12.955849] [drm] Detected VRAM RAM=128M, BAR=128M
[   12.955856] [drm] RAM width 128bits DDR
[   12.956174] [TTM] Zone  kernel: Available graphics memory: 443594 kiB.
[   12.956179] [TTM] Zone highmem: Available graphics memory: 513198 kiB.
[   12.956206] [drm] radeon: 128M of VRAM memory ready
[   12.956210] [drm] radeon: 128M of GTT memory ready.
[   12.956463] [drm] radeon: 1 quad pipes, 1 Z pipes initialized.
[   12.956483] [drm] radeon: cp idle (0x10000C03)
[   12.956571] [drm] Loading R300 Microcode
[   12.956578] platform radeon_cp.0: firmware: requesting radeon/R300_cp.bin
[   13.538719] [drm] radeon: ring at 0x00000000E0000000
[   13.538745] [drm] ring test succeeded in 0 usecs
[   13.547031] [drm] radeon: ib pool ready.
[   13.547155] [drm] ib test succeeded in 0 usecs
[   13.549206] [drm] Default TV standard: NTSC
[   13.549211] [drm] 27.000000000 MHz TV ref clk
[   13.550456] [drm] Default TV standard: NTSC
[   13.550461] [drm] 27.000000000 MHz TV ref clk
[   13.550696] [drm] Radeon Display Connectors
[   13.550701] [drm] Connector 0:
[   13.550704] [drm]   VGA
[   13.550709] [drm]   DDC: 0x60 0x60 0x60 0x60 0x60 0x60 0x60 0x60
[   13.550713] [drm]   Encoders:
[   13.550716] [drm]     CRT1: INTERNAL_DAC1
[   13.550720] [drm] Connector 1:
[   13.550723] [drm]   VGA
[   13.550727] [drm]   DDC: 0x64 0x64 0x64 0x64 0x64 0x64 0x64 0x64
[   13.550731] [drm]   Encoders:
[   13.550734] [drm]     CRT2: INTERNAL_DAC2
[   13.550738] [drm] Connector 2:
[   13.550741] [drm]   S-video
[   13.550744] [drm]   Encoders:
[   13.550747] [drm]     TV1: INTERNAL_DAC2
[   13.608383] radeon 0000:01:00.0: The number of extension(32) is over max (4), actually read number (4)
[   13.780280]   alloc irq_desc for 17 on node -1
[   13.780287]   alloc kstat_irqs on node -1
[   13.780301] Intel ICH 0000:00:1f.5: PCI INT B -> GSI 17 (level, low) -> IRQ 17
[   13.780356] Intel ICH 0000:00:1f.5: setting latency timer to 64
[   13.982559] i2c i2c-0: sendbytes: NAK bailout.
[   13.982665] [drm:radeon_vga_detect] *ERROR* VGA-1: probed a monitor but no|invalid EDID
[   13.983523] i2c i2c-0: sendbytes: NAK bailout.
[   14.104024] intel8x0_measure_ac97_clock: measured 54450 usecs (2624 samples)
[   14.104028] intel8x0: clocking to 48000
[   14.201992] [drm] 2: conflicting encoders switching off SVIDEO-1
[   14.201999] [drm] in favor of VGA-2
[   14.217891] [drm] fb mappable at 0xE8040000
[   14.217896] [drm] vram apper at 0xE8000000
[   14.217900] [drm] size 3145728
[   14.217903] [drm] fb depth is 24
[   14.217906] [drm]    pitch is 4096
[   14.218074] fb0: radeondrmfb frame buffer device
[   14.218078] registered panic notifier
[   14.218088] [drm] Initialized radeon 2.0.0 20080528 for 0000:01:00.0 on minor 0
[   14.238626] vga16fb: initializing
[   14.238635] vga16fb: mapped to 0xc00a0000
[   14.238644] vga16fb: not registering due to another framebuffer present
[   14.392254] Console: switching to colour frame buffer device 128x48
[   14.430241] i2c i2c-0: sendbytes: NAK bailout.
[   14.430470] [drm:radeon_vga_detect] *ERROR* VGA-1: probed a monitor but no|invalid EDID
[   14.431538] i2c i2c-0: sendbytes: NAK bailout.