My Ubuntu 10.04 display freezes at random intervals of time

My Ubuntu 10.04(Lucid lynx) has ithe display screen going blank and needs reboot at certain times.
Attached is the syslog.
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Dec 31 23:56:35 samurai gdm-session-worker[984]: WARNING: Unable to load file '/etc/gdm/custom.conf': No such file or directory
Dec 31 23:56:36 samurai rtkit-daemon[992]: Sucessfully called chroot.
Dec 31 23:56:36 samurai rtkit-daemon[992]: Sucessfully dropped privileges.
Dec 31 23:56:36 samurai rtkit-daemon[992]: Sucessfully limited resources.
Dec 31 23:56:36 samurai rtkit-daemon[992]: Running.
Dec 31 23:56:36 samurai rtkit-daemon[992]: Watchdog thread running.
Dec 31 23:56:36 samurai rtkit-daemon[992]: Canary thread running.
Dec 31 23:56:36 samurai polkitd[996]: started daemon version 0.96 using authority implementation `local' version `0.96'
Dec 31 23:56:36 samurai anacron[1021]: Anacron 2.3 started on 2010-12-31
Dec 31 23:56:37 samurai anacron[1021]: Normal exit (0 jobs run)
Dec 31 23:56:37 samurai rtkit-daemon[992]: Sucessfully made thread 990 of process 990 (n/a) owned by '112' high priority at nice level -11.
Dec 31 23:56:37 samurai rtkit-daemon[992]: Supervising 1 threads of 1 processes of 1 users.
Dec 31 23:56:37 samurai rtkit-daemon[992]: Sucessfully made thread 1051 of process 990 (n/a) owned by '112' RT at priority 5.
Dec 31 23:56:37 samurai rtkit-daemon[992]: Supervising 2 threads of 1 processes of 1 users.
Dec 31 23:56:38 samurai dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
Dec 31 23:56:38 samurai rtkit-daemon[992]: Sucessfully made thread 1052 of process 990 (n/a) owned by '112' RT at priority 5.
Dec 31 23:56:38 samurai rtkit-daemon[992]: Supervising 3 threads of 1 processes of 1 users.
Dec 31 23:56:38 samurai pulseaudio[990]: module-alsa-card.c: Failed to find a working profile.
Dec 31 23:56:38 samurai pulseaudio[990]: module.c: Failed to load module "module-alsa-card" (argument: "device_id="1" name="1" card_name="alsa_card.1" tsched=yes ignore_dB=no card_properties="module-udev-detect.discovered=1""): initialization failed.
Dec 31 23:56:38 samurai gdm-simple-greeter[982]: Gtk-WARNING: /build/buildd/gtk+2.0-2.20.1/gtk/gtkwidget.c:5636: widget not within a GtkWindow
Dec 31 23:56:39 samurai acpid: client connected from 1070[107:114]
Dec 31 23:56:39 samurai acpid: 1 client rule loaded
Dec 31 23:56:43 samurai pulseaudio[990]: ratelimit.c: 3 events suppressed
Dec 31 23:56:43 samurai gdm-session-worker[984]: GLib-GObject-CRITICAL: g_value_get_boolean: assertion `G_VALUE_HOLDS_BOOLEAN (value)' failed
Dec 31 23:56:46 samurai dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 14
Dec 31 23:56:51 samurai rtkit-daemon[992]: Sucessfully made thread 1172 of process 1172 (n/a) owned by '1000' high priority at nice level -11.
Dec 31 23:56:51 samurai rtkit-daemon[992]: Supervising 4 threads of 2 processes of 2 users.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Sucessfully made thread 1182 of process 1172 (n/a) owned by '1000' RT at priority 5.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Supervising 5 threads of 2 processes of 2 users.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Sucessfully made thread 1186 of process 1172 (n/a) owned by '1000' RT at priority 5.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Supervising 6 threads of 2 processes of 2 users.
Dec 31 23:56:53 samurai pulseaudio[1172]: module-alsa-card.c: Failed to find a working profile.
Dec 31 23:56:53 samurai pulseaudio[1172]: module.c: Failed to load module "module-alsa-card" (argument: "device_id="1" name="1" card_name="alsa_card.1" tsched=yes ignore_dB=no card_properties="module-udev-detect.discovered=1""): initialization failed.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Sucessfully made thread 1189 of process 1189 (n/a) owned by '1000' high priority at nice level -11.
Dec 31 23:56:53 samurai rtkit-daemon[992]: Supervising 7 threads of 3 processes of 2 users.
Dec 31 23:56:53 samurai pulseaudio[1189]: pid.c: Daemon already running.
Dec 31 23:56:58 samurai pulseaudio[1172]: ratelimit.c: 8 events suppressed
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I had installed 9.04(karmic Kola) and upgraded to 10.04
System configuration
Intel Celeron 2.53Ghz, 256 MB RAM, 40 GB HDD
WindowsXP and Ubuntu 10.04 dual boot

Is this a known issue with 10.04?