Hi - I'm new to this, so apologies if I'm being daft. I get this same result when trying to start up Vegastrike using a an ATI 9 series card, thus:

. . . blah, blah, blah

Loading a starsystem
Loading Star System Crucible/Cephid_17
 Next To: Crucible/17-ar
 Next To: Crucible/Cardell
 Next To: Crucible/Cephid_17
 Next To: Crucible/Enyo
 Next To: Crucible/Cephid_17
 Next To: Crucible/OldzieyLoading active missions True
drmRadeonCmdBuffer: -12. Kernel failed to parse or rejected command stream. See dmesg for more info.
AL lib: ALc.c:1253: exit() 1 device(s) and 1 context(s) NOT deleted
AL lib: alSource.c:2291: alcDestroyContext(): 32 Source(s) NOT deleted
AL lib: alBuffer.c:1097: exit() 16 Buffer(s) NOT deleted

dmesg:

after a fair bit of blah blah blah,

[    6.744269] fb0: radeondrmfb frame buffer device
[    6.744274] registered panic notifier
[    6.744284] [drm] Initialized radeon 2.0.0 20080528 for 0000:01:00.0 on minor 0
[    6.851022] vga16fb: initializing
[    6.851027] vga16fb: mapped to 0xc00a0000
[    6.851033] vga16fb: not registering due to another framebuffer present
[    7.690852]   alloc irq_desc for 17 on node -1
[    7.690856]   alloc kstat_irqs on node -1
[    7.690866] Intel ICH 0000:00:1f.5: PCI INT B -> GSI 17 (level, low) -> IRQ 17
[    7.690916] Intel ICH 0000:00:1f.5: setting latency timer to 64
[    7.714135] Console: switching to colour frame buffer device 128x48
[    8.028044] intel8x0_measure_ac97_clock: measured 54423 usecs (2622 samples)
[    8.028049] intel8x0: clocking to 48000
[    8.784948] type=1505 audit(1286356674.706:5):  operation="profile_load" pid=644 name="/usr/share/gdm/guest-session/Xsession"
[    8.789271] type=1505 audit(1286356674.710:6):  operation="profile_replace" pid=647 name="/sbin/dhclient3"
[    8.789844] type=1505 audit(1286356674.710:7):  operation="profile_replace" pid=647 name="/usr/lib/NetworkManager/nm-dhcp-client.action"
[    8.790161] type=1505 audit(1286356674.710:8):  operation="profile_replace" pid=647 name="/usr/lib/connman/scripts/dhclient-script"
[    9.882622] type=1505 audit(1286356675.802:9):  operation="profile_load" pid=649 name="/usr/bin/evince"
[    9.890537] type=1505 audit(1286356675.810:10):  operation="profile_load" pid=649 name="/usr/bin/evince-previewer"
[    9.895433] type=1505 audit(1286356675.814:11):  operation="profile_load" pid=649 name="/usr/bin/evince-thumbnailer"
[   10.006663] type=1505 audit(1286356675.926:12):  operation="profile_load" pid=654 name="/usr/lib/cups/backend/cups-pdf"
[   10.007321] type=1505 audit(1286356675.926:13):  operation="profile_load" pid=654 name="/usr/sbin/cupsd"
[   10.024698] type=1505 audit(1286356675.946:14):  operation="profile_load" pid=655 name="/usr/sbin/tcpdump"
[   10.816940] eth0: link up, 100Mbps, full-duplex, lpa 0x45E1
[   16.650169] i2c i2c-0: sendbytes: NAK bailout.
[   21.204025] eth0: no IPv6 routers present
[ 5373.646201] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!
[ 5527.210871] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!
[ 6928.308771] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!
[11409.283978] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!

Don't know if this helps.

I'm going to try and use the closed source driver and see if that works.

Bill