Sadly it's 11.04 now. I still suffered from this bug. I am working on Ubuntu 11.04 Beta2 with nouveau 3D driver.
The system halts any time.

Here is part of Xorg.0.log

[    25.681] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    25.681] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    25.681] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    26.019] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    26.019] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    26.019] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    26.376] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    26.376] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    26.376] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    26.712] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    26.712] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    26.712] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    37.241] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    37.241] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    37.241] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    37.577] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    37.577] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    37.577] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    37.912] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    37.912] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    37.912] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    38.248] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    38.248] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    38.248] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[    39.901] (II) NOUVEAU(0): EDID vendor "SEC", prod id 12368
[    39.901] (II) NOUVEAU(0): Printing DDC gathered Modelines:
[    39.901] (II) NOUVEAU(0): Modeline "1366x768"x0.0   72.33  1366 1414 1446 1526  768 770 775 790 -hsync -vsync (47.4 kHz)
[ 22727.289] [mi] EQ overflowing. The server is probably stuck in an infinite loop.
[ 22727.289] 
Backtrace:
[ 22727.299] 0: /usr/bin/X (xorg_backtrace+0x26) [0x4a2626]
[ 22727.299] 1: /usr/bin/X (mieqEnqueue+0x1f4) [0x4a18e4]
[ 22727.299] 2: /usr/bin/X (xf86PostMotionEventM+0x97) [0x47d767]
[ 22727.299] 3: /usr/lib/xorg/modules/input/evdev_drv.so (0x7f3a69e9e000+0x5ff3) [0x7f3a69ea3ff3]
[ 22727.299] 4: /usr/lib/xorg/modules/input/evdev_drv.so (0x7f3a69e9e000+0x668d) [0x7f3a69ea468d]
[ 22727.299] 5: /usr/bin/X (0x400000+0x6c657) [0x46c657]
[ 22727.299] 6: /usr/bin/X (0x400000+0x124bbe) [0x524bbe]
[ 22727.300] 7: /lib/x86_64-linux-gnu/libpthread.so.0 (0x7f3a6f3fc000+0xfc60) [0x7f3a6f40bc60]
[ 22727.300] 8: /lib/x86_64-linux-gnu/libc.so.6 (ioctl+0x7) [0x7f3a6e404297]
[ 22727.300] 9: /lib/x86_64-linux-gnu/libdrm.so.2 (drmIoctl+0x28) [0x7f3a6c99e058]
[ 22727.300] 10: /lib/x86_64-linux-gnu/libdrm.so.2 (drmCommandWrite+0x1b) [0x7f3a6c9a030b]
[ 22727.300] 11: /lib/x86_64-linux-gnu/libdrm_nouveau.so.1 (0x7f3a6c35b000+0x2b87) [0x7f3a6c35db87]
[ 22727.300] 12: /lib/x86_64-linux-gnu/libdrm_nouveau.so.1 (nouveau_bo_map_range+0xfe) [0x7f3a6c35e19e]
[ 22727.300] 13: /lib/x86_64-linux-gnu/libdrm_nouveau.so.1 (0x7f3a6c35b000+0x1c2d) [0x7f3a6c35cc2d]
[ 22727.300] 14: /lib/x86_64-linux-gnu/libdrm_nouveau.so.1 (nouveau_pushbuf_flush+0x1ae) [0x7f3a6c35d22e]
[ 22727.300] 15: /usr/lib/xorg/modules/libexa.so (0x7f3a6b90d000+0x9015) [0x7f3a6b916015]
[ 22727.300] 16: /usr/lib/xorg/modules/libexa.so (0x7f3a6b90d000+0xbba1) [0x7f3a6b918ba1]
[ 22727.300] 17: /usr/bin/X (0x400000+0xdcab9) [0x4dcab9]
[ 22727.300] 18: /usr/lib/xorg/modules/libexa.so (0x7f3a6b90d000+0xd1c1) [0x7f3a6b91a1c1]
[ 22727.300] 19: /usr/bin/X (0x400000+0xdc1b5) [0x4dc1b5]
[ 22727.300] 20: /usr/bin/X (0x400000+0xd5638) [0x4d5638]
[ 22727.300] 21: /usr/bin/X (0x400000+0x2e2a9) [0x42e2a9]
[ 22727.300] 22: /usr/bin/X (0x400000+0x21a7e) [0x421a7e]
[ 22727.300] 23: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xff) [0x7f3a6e345eff]
[ 22727.300] 24: /usr/bin/X (0x400000+0x21629) [0x421629]