[Résolu] Problème ralentissement

Bonjour,
Aprés mise à jour Xubuntu par gestionnaire de mise à jour de 14.04 vers 14.10 (dernière version)
je constate un ralentissement très important .

Ma config Xubuntu:
Linux pc-famille 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13 17:56:26 UTC 2014 i686 athlon i686 GNU/Linux

Affichage avec dmesg|tail :

[ 74.414275] type=1400 audit(1423825508.826:13): apparmor="STATUS" operation="profile_load" profile="unconfined" name="/usr/bin/evince" pid=894 comm="apparmor_parser"
[ 74.414287] type=1400 audit(1423825508.826:14): apparmor="STATUS" operation="profile_load" profile="unconfined" name="sanitized_helper" pid=894 comm="apparmor_parser"
[ 74.560067] systemd-logind[924]: New seat seat0.
[ 74.587592] systemd-logind[924]: Watching system buttons on /dev/input/event1 (Power Button)
[ 74.587673] systemd-logind[924]: Watching system buttons on /dev/input/event0 (Power Button)
[ 78.618153] vboxdrv: module verification failed: signature and/or required key missing - tainting kernel
[ 78.626250] vboxdrv: Found 1 processor cores.
[ 78.632159] vboxdrv: TSC mode is 'synchronous', kernel timer mode is 'normal'.
[ 78.632163] vboxdrv: Successfully loaded version 4.3.20 (interface 0x001a0008).
[ 78.950352] vboxpci: IOMMU not found (not registered)
[ 80.278290] init: plymouth-upstart-bridge main process ended, respawning
[ 80.469077] systemd-logind[924]: Failed to start unit user@112.service: Unknown unit: user@112.service
[ 80.469087] systemd-logind[924]: Failed to start user service: Unknown unit: user@112.service
[ 80.474928] systemd-logind[924]: New session c1 of user lightdm.
[ 80.474962] systemd-logind[924]: Linked /tmp/.X11-unix/X0 to /run/user/112/X11-display.
[ 90.220525] systemd-logind[924]: Failed to start unit user@1001.service: Unknown unit: user@1001.service
[ 90.220536] systemd-logind[924]: Failed to start user service: Unknown unit: user@1001.service
[ 90.227826] systemd-logind[924]: New session c2 of user monmich.
[ 90.227858] systemd-logind[924]: Linked /tmp/.X11-unix/X0 to /run/user/1001/X11-display.

Apparemment ce serait un problème de connexion à la session ou de service ?
Merci pour les explications etla solution possible,