Hi Joseph,
  this still occurs for me with the 3.5.7 from that link (and with current raring), but as stated not with the 3.5.0-19 from quantal.
My test procedure on my box is:
  * Fresh boot
  * Log in via kdm as my default user
  * Wait for my standard KDE desktop to settle
  * K menu->Leave->Switch user
     * select new session
     * Login as my other user
As my other user:
  * K menu->Leave->Switchuser
  * select the existing session for my main user

And that blew up this time for both 3.7.0-7-generic #15-Ubuntu and 3.5.7-030507-generic #201210130556

and I've checked again, 3.5.0-7 is still good for me - bounced back and forward 5 or 6 times.

I also had a blow up on 3.7.0 when running an SDL game, also triggered the -35

dmesg on the blowups from the user switching test:
3.7.0-7-generic #15-Ubuntu booted, logged in, did switch user, did switch back
   - bang 
[   72.399456] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -35!
[   72.415838] radeon 0000:07:00.0: GPU reset succeeded, trying to resume
[   72.421887] [drm] probing gen 2 caps for device 8086:d138 = 2/0
[   72.421890] [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[   72.424721] [drm] PCIE GART of 512M enabled (table at 0x0000000000040000).
[   72.424812] radeon 0000:07:00.0: WB enabled
[   72.424820] radeon 0000:07:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and cpu addr 0xffff880225f0ac00
[   72.471175] [drm] ring test on 0 succeeded in 1 usecs
[   72.671008] [drm] ib test on ring 0 succeeded in 0 usecs
[   72.671029] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -35!
[   72.687120] radeon 0000:07:00.0: Saved 25 dwords of commands on ring 0.
[   72.687126] radeon 0000:07:00.0: GPU softreset 
[   72.687131] radeon 0000:07:00.0:   R_008010_GRBM_STATUS=0xA0003028
[   72.687134] radeon 0000:07:00.0:   R_008014_GRBM_STATUS2=0x00000002
[   72.687138] radeon 0000:07:00.0:   R_000E50_SRBM_STATUS=0x200000C0
[   72.687142] radeon 0000:07:00.0:   R_008674_CP_STALLED_STAT1 = 0x00000000
[   72.687146] radeon 0000:07:00.0:   R_008678_CP_STALLED_STAT2 = 0x00010000
[   72.687149] radeon 0000:07:00.0:   R_00867C_CP_BUSY_STAT     = 0x00000000
[   72.687153] radeon 0000:07:00.0:   R_008680_CP_STAT          = 0x80010042
[   72.687160] radeon 0000:07:00.0:   R_008020_GRBM_SOFT_RESET=0x00007FEE
[   72.702019] radeon 0000:07:00.0: R_008020_GRBM_SOFT_RESET=0x00000001
[   72.717870] radeon 0000:07:00.0:   R_008010_GRBM_STATUS=0x00003028
[   72.717874] radeon 0000:07:00.0:   R_008014_GRBM_STATUS2=0x00000002
[   72.717878] radeon 0000:07:00.0:   R_000E50_SRBM_STATUS=0x200000C0
[   72.717882] radeon 0000:07:00.0:   R_008674_CP_STALLED_STAT1 = 0x00000000
[   72.717885] radeon 0000:07:00.0:   R_008678_CP_STALLED_STAT2 = 0x00000000
[   72.717889] radeon 0000:07:00.0:   R_00867C_CP_BUSY_STAT     = 0x00000000
[   72.717892] radeon 0000:07:00.0:   R_008680_CP_STAT          = 0x00000000
[   72.718887] radeon 0000:07:00.0: GPU reset succeeded, trying to resume
[   72.720137] [drm] probing gen 2 caps for device 8086:d138 = 2/0
[   72.720139] [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[   72.723035] [drm] PCIE GART of 512M enabled (table at 0x0000000000040000).
[   72.723111] radeon 0000:07:00.0: WB enabled
[   72.723116] radeon 0000:07:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and cpu addr 0xffff880225f0ac00
[   72.769446] [drm] ring test on 0 succeeded in 1 usecs


3.5.7-030507-generic #201210130556

[   68.691631] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -35!
[   68.707534] radeon 0000:07:00.0: GPU reset succeed
[   68.725808] [drm] PCIE GART of 512M enabled (table at 0x0000000000040000).
[   68.725853] radeon 0000:07:00.0: WB enabled
[   68.725855] radeon 0000:07:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and cpu addr 0xffff880226b02c00
[   68.771991] [drm] ring test on 0 succeeded in 1 usecs
[   68.772019] [drm] ib test on ring 0 succeeded in 0 usecs
[   69.368943] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -35!