When I am explore thinks on the harddrive with dolphin file manager, some times it just crashes and my laptop freeses, al I can do is hold the power button and restart.... What is wrong why is this? I have a syslog:

Code:
Jul  7 21:16:32 bt dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 6
Jul  7 21:16:38 bt dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 14
Jul  7 21:16:52 bt dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 15
Jul  7 21:17:01 bt CRON[1724]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jul  7 21:17:07 bt dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 18
Jul  7 21:17:25 bt dhclient: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
Jul  7 21:17:33 bt dhclient: No DHCPOFFERS received.
Jul  7 21:17:33 bt dhclient: No working leases in persistent database - sleeping.
Jul  7 21:18:16 bt kernel: [  377.675615] [drm] Resetting GPU
Jul  7 21:19:07 bt kernel: imklog 4.2.0, log source = /proc/kmsg started.
Jul  7 21:19:07 bt rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="675" x-info="http://www.rsyslog.com"] (re)start
Jul  7 21:19:07 bt rsyslogd: rsyslogd's groupid changed to 103
Jul  7 21:19:07 bt rsyslogd: rsyslogd's userid changed to 101
Jul  7 21:19:07 bt rsyslogd-2039: Could no open output file '/dev/xconsole' [try http://www.rsyslog.com/e/2039 ]
Jul  7 21:19:07 bt kernel: [    0.000000] Initializing cgroup subsys cpuset
Jul  7 21:19:07 bt kernel: [    0.000000] Initializing cgroup subsys cpu
Jul  7 21:19:07 bt kernel: [    0.000000] Linux version 2.6.38 (root@bt) (gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) ) #1 SMP Thu Mar 17 22:59:29 EDT 2011
Jul  7 21:19:07 bt kernel: [    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-2.6.38 root=UUID=17d996c1-699c-4f0c-9438-1bb5123b299d ro text splash nomodeset vga=791
Jul  7 21:19:07 bt kernel: [    0.000000] BIOS-provided physical RAM map:
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000000d2000 - 00000000000d4000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000000d8000 - 00000000000e0000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000000e4000 - 0000000000100000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 0000000000100000 - 00000000bdaa1000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdaa1000 - 00000000bdaa7000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdaa7000 - 00000000bdbbc000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdbbc000 - 00000000bdc0f000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdc0f000 - 00000000bdd08000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdd08000 - 00000000bdf0f000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdf0f000 - 00000000bdf19000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdf19000 - 00000000bdf1f000 (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdf1f000 - 00000000bdf64000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdf64000 - 00000000bdf9f000 (ACPI NVS)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdf9f000 - 00000000bdfe2000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdfe2000 - 00000000bdfff000 (ACPI data)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 00000000bdfff000 - 00000000be000000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000]  BIOS-e820: 0000000100000000 - 0000000140000000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000] NX (Execute Disable) protection: active
Jul  7 21:19:07 bt kernel: [    0.000000] DMI present.
Jul  7 21:19:07 bt kernel: [    0.000000] DMI: TOSHIBA Satellite L500/KSWAA, BIOS V2.10 05/06/2010
Jul  7 21:19:07 bt kernel: [    0.000000] e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved)
Jul  7 21:19:07 bt kernel: [    0.000000] e820 remove range: 00000000000a0000 - 0000000000100000 (usable)
Jul  7 21:19:07 bt kernel: [    0.000000] No AGP bridge found
Jul  7 21:19:07 bt kernel: [    0.000000] last_pfn = 0x140000 max_arch_pfn = 0x400000000
Jul  7 21:19:07 bt kernel: [    0.000000] MTRR default type: uncachable
Jul  7 21:19:07 bt kernel: [    0.000000] MTRR fixed ranges enabled:
Jul  7 21:19:07 bt kernel: [    0.000000]   00000-9FFFF write-back
Jul  7 21:19:07 bt kernel: [    0.000000]   A0000-BFFFF uncachable
Jul  7 21:19:07 bt kernel: [    0.000000]   C0000-D3FFF write-protect
Jul  7 21:19:07 bt kernel: [    0.000000]   D4000-DBFFF uncachable
Jul  7 21:19:07 bt kernel: [    0.000000]   DC000-FFFFF write-protect
Jul  7 21:19:07 bt kernel: [    0.000000] MTRR variable ranges enabled:
Jul  7 21:19:07 bt kernel: [    0.000000]   0 base 000000000 mask F80000000 write-back
Jul  7 21:19:07 bt kernel: [    0.000000]   1 base 080000000 mask FC0000000 write-back
Jul  7 21:19:07 bt kernel: [    0.000000]   2 base 100000000 mask FC0000000 write-back
Jul  7 21:19:07 bt kernel: [    0.000000]   3 base 0FFE00000 mask FFFF80000 write-protect
Jul  7 21:19:07 bt kernel: [    0.000000]   4 disabled
Jul  7 21:19:07 bt kernel: [    0.000000]   5 disabled

(..) cutted for to much words