I have observed this bug also on Ubuntu 10.04 (Details below):

[…]
(II) NOUVEAU(0): Modeline "1152x864"x0.0  108.00  1152 1216 1344 1600  864 865 868 900 +hsync +vsync (67.5 kHz)
(II) NOUVEAU(0): Modeline "1400x1050"x0.0  156.00  1400 1504 1648 1896  1050 1053 1057 1099 -hsync +vsync (82.3 kHz)
(II) NOUVEAU(0): Modeline "1440x900"x0.0  106.50  1440 1520 1672 1904  900 903 909 934 -hsync +vsync (55.9 kHz)
(II) NOUVEAU(0): Modeline "1440x900"x0.0  136.75  1440 1536 1688 1936  900 903 909 942 -hsync +vsync (70.6 kHz)
(II) NOUVEAU(0): Modeline "1680x1050"x0.0  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync (65.3 kHz)
[mi] EQ overflowing. The server is probably stuck in an infinite loop.

Backtrace:
0: /usr/bin/X (xorg_backtrace+0x28) [0x4a3248]
1: /usr/bin/X (mieqEnqueue+0x1f4) [0x4a2ac4]
2: /usr/bin/X (xf86PostMotionEventP+0xc4) [0x47cea4]
3: /usr/lib/xorg/modules/input/evdev_drv.so (0x7f5182f10000+0x53cf) [0x7f5182f153cf]
4: /usr/bin/X (0x400000+0x6fca7) [0x46fca7]
5: /usr/bin/X (0x400000+0x11d1f3) [0x51d1f3]
6: /lib/libpthread.so.0 (0x7f518823e000+0xf8f0) [0x7f518824d8f0]
7: /lib/libc.so.6 (ioctl+0x7) [0x7f5186ff6157]
8: /lib/libdrm.so.2 (drmIoctl+0x28) [0x7f51855a75b8]
9: /lib/libdrm.so.2 (drmCommandWrite+0x1b) [0x7f51855a783b]
10: /lib/libdrm_nouveau.so.1 (0x7f5184f69000+0x2f7d) [0x7f5184f6bf7d]
11: /lib/libdrm_nouveau.so.1 (nouveau_bo_map_range+0xfc) [0x7f5184f6c1bc]
12: /lib/libdrm_nouveau.so.1 (0x7f5184f69000+0x2166) [0x7f5184f6b166]
13: /lib/libdrm_nouveau.so.1 (nouveau_pushbuf_flush+0x29c) [0x7f5184f6b4fc]
14: /usr/lib/xorg/modules/libexa.so (0x7f51840c4000+0x8876) [0x7f51840cc876]
15: /usr/lib/xorg/modules/libexa.so (0x7f51840c4000+0x9415) [0x7f51840cd415]
16: /usr/bin/X (0x400000+0xd8a7b) [0x4d8a7b]
17: /usr/bin/X (0x400000+0x2ebb4) [0x42ebb4]
18: /usr/bin/X (0x400000+0x30c3c) [0x430c3c]
19: /usr/bin/X (0x400000+0x261aa) [0x4261aa]
20: /lib/libc.so.6 (__libc_start_main+0xfd) [0x7f5186f36c4d]
21: /usr/bin/X (0x400000+0x25d59) [0x425d59]

strace shows tons of this:

[…]
--- SIGALRM (Alarm clock) @ 0 (0) ---
rt_sigreturn(0xe)                       = -1 EINTR (Interrupted system call)
ioctl(8, 0x40086485, 0x7fff98e3a6d0)    = ? ERESTARTSYS (To be restarted)
--- SIGALRM (Alarm clock) @ 0 (0) ---
rt_sigreturn(0xe)                       = -1 EINTR (Interrupted system call)
ioctl(8, 0x40086485, 0x7fff98e3a6d0)    = ? ERESTARTSYS (To be restarted)
--- SIGALRM (Alarm clock) @ 0 (0) ---
rt_sigreturn(0xe)                       = -1 EINTR (Interrupted system call)
ioctl(8, 0x40086485, 0x7fff98e3a6d0)    = ? ERESTARTSYS (To be restarted)
--- SIGALRM (Alarm clock) @ 0 (0) ---
rt_sigreturn(0xe)                       = -1 EINTR (Interrupted system call)
ioctl(8, 0x40086485, 0x7fff98e3a6d0)    = ? ERESTARTSYS (To be restarted)
[…]

neper:~# uname -a
Linux neper 2.6.32-22-generic #33-Ubuntu SMP Wed Apr 28 13:28:05 UTC 2010 x86_64 GNU/Linux
neper:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 10.04 LTS
Release:        10.04
Codename:       lucid
neper:~# dpkg -l | fgrep nouveau
ii  libdrm-nouveau1             2.4.18-1ubuntu3                        […]
ii  xserver-xorg-video-nouveau  1:0.0.15+git20100219+9b4118d-0ubuntu5  […]
neper:~# dpkg -l | egrep 'xserver-xorg( |-core)'
ii  xserver-xorg                1:7.5+5ubuntu1                         […]
ii  xserver-xorg-core           2:1.7.6-2ubuntu7                       […]
neper:~# lspci | fgrep VGA
01:00.0 VGA compatible controller: nVidia Corporation GT218 [GeForce 210] (rev a2)
neper:~#