Mon macbook air se fige tout seul

Question

Bonjour a tous,
Mon macbook se fige tout seul. Je suis sous OS X moutain lion 10.8.2
Processeur : 1,8 Ghz Intel Core i5
Memoire : 4Go 1600 MHz DDR3.
Sur les conseils du support telephonique apple j'ai effacé mon disque (sauvegarde au préalable de mes data sur une Timecapsule)  et reinstaller l OS et refait une mise à jour de l OS pour me remettre sur la dernière version 10.8.2.
Je n'ai fait aucune installation supplementaire (mis à part itunes et utilitaire airport (mis à jour et proposé par apple store)).
le mac se fige qu'importe ce que je fait dessus.
Un exemple, ce soir à 20h23  il se fige (donc l'horloge se fige) voici pour information la console (ci-dessous)
Avez vous deja rencontré ce probleme?
Merci à tous pour votre aide .
22/02/13 19:59:53,280 com.apple.SecurityServer[15]: Session 100002 created
22/02/13 20:01:18,095 WindowServer[71]: CGXDisableUpdate: UI updates were forcibly disabled by application "Safari" for over 1.00 seconds. Server has re-enabled them.
22/02/13 20:01:18,404 WindowServer[71]: reenable_update_for_connection: UI updates were finally reenabled by application "Safari" after 1.31 seconds (server forcibly re-enabled them after 1.00 seconds)
22/02/13 20:01:20,083 WebProcess[215]: objc[215]: Object 0x7f9a98c1c7e0 of class NSUserDefaults autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug
22/02/13 20:01:20,091 WebProcess[215]: objc[215]: Object 0x7f9a98c1c7e0 of class NSUserDefaults autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug
22/02/13 20:01:41,273 WebProcess[215]: objc[215]: Object 0x7f9a98c1c7e0 of class NSUserDefaults autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug
22/02/13 20:01:41,274 WebProcess[215]: objc[215]: Object 0x7f9a98c1c7e0 of class NSUserDefaults autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug
22/02/13 20:01:41,274 WebProcess[215]: objc[215]: Object 0x7f9a98c1c7e0 of class NSUserDefaults autoreleased with no pool in place - just leaking - break on objc_autoreleaseNoPool() to debug
22/02/13 20:12:36,867 Safari[213]: CGContextClipToRect: invalid context 0x0
22/02/13 20:15:47,331 WebProcess[215]: <CATransformLayer: 0x7f9a99815af0> - changing property shadowOffset in transform-only layer, will have no effect
22/02/13 20:15:47,331 WebProcess[215]: <CATransformLayer: 0x7f9a99815af0> - changing property shadowColor in transform-only layer, will have no effect
22/02/13 20:15:47,332 WebProcess[215]: <CATransformLayer: 0x7f9a99815af0> - changing property shadowRadius in transform-only layer, will have no effect
22/02/13 20:15:47,332 WebProcess[215]: <CATransformLayer: 0x7f9a9eae73f0> - changing property shadowOffset in transform-only layer, will have no effect
22/02/13 20:15:47,332 WebProcess[215]: <CATransformLayer: 0x7f9a9eae73f0> - changing property shadowColor in transform-only layer, will have no effect
22/02/13 20:15:47,333 WebProcess[215]: <CATransformLayer: 0x7f9a9eae73f0> - changing property shadowRadius in transform-only layer, will have no effect
22/02/13 20:22:30,000 kernel[0]: MacAuthEvent en0   Auth result for: 20:c9:d0:23:d5:6a  MAC AUTH succeeded
22/02/13 20:22:30,000 kernel[0]: wlEvent: en0 en0 Link UP virtIf = 0
22/02/13 20:22:30,000 kernel[0]: AirPort: RSN handshake complete on en0
22/02/13 20:22:30,000 kernel[0]: wl0: Roamed or switched channel, reason #8, bssid 20:c9:d0:23:d5:6a
22/02/13 20:22:30,000 kernel[0]: en0: BSSID changed to 20:c9:d0:23:d5:6a
22/02/13 20:22:30,000 kernel[0]: en0::IO80211Interface::postMessage bssid changed
22/02/13 20:38:56,000 bootlog[0]: BOOT_TIME 1361561936 0

Answer 1

The next time you have the problem, note the exact times when it starts and ends: hour, minute, second.
If you have more than one user account, these instructions must be carried out as an administrator.
Launch the Console application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Console in the page that opens.
Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.
Scroll back in the log to the time you noted above. Post any messages timestamped during that interval – the text, please, not a screenshot.
When posting a log extract, be selective. In most cases, a few dozen lines are more than enough.
DO NOT INDISCRIMINATELY DUMP THOUSANDS OF LINES FROM THE LOG INTO A MESSAGE. If you do that, I will not respond.
Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.