Ao que tudo indica, o problema esta no seu processador que não aguenta o "tranco", talvez tunando o sistema de arquivos (como ensina o galactus), diminuindo o numero de processos (para aliviar o processador) esse problema diminua consideravelmente.
Para saber as resoluções compatíveis com o seu monitor, rode os comandos
sudo apt-get update && sudo apt-get install v86d hwinfo
e depois
sudo hwinfo --framebuffer
athosbr99@athosbr99-Aspire-5732Z:~$ sudo hwinfo --framebuffer
> hal.1: read hal dataprocess 10015: arguments to dbus_move_error() were incorrect, assertion "(dest) == NULL || !dbus_error_is_set ((dest))" failed in file dbus-errors.c line 280.
This is normally a bug in some application using the D-Bus library.
libhal.c 3483 : Error unsubscribing to signals, error=The name org.freedesktop.Hal was not provided by any .service files
02: None 00.0: 11001 VESA Framebuffer
[Created at bios.464]
Unique ID: rdCR.fRULN9k9OD4
Hardware Class: framebuffer
Model: "Intel(r)Cantiga Graphics Controller"
Vendor: "Intel Corporation"
Device: "Intel(r)Cantiga Graphics Controller"
SubVendor: "Intel(r)Cantiga Graphics Chip Accelerated VGA BIOS"
SubDevice:
Revision: "Hardware Version 0.0"
Memory Size: 63 MB + 960 kB
Memory Range: 0xc0000000-0xc3feffff (rw)
Mode 0x0305: 1024x768 (+1024), 8 bits
Mode 0x0317: 1024x768 (+2048), 16 bits
Mode 0x0318: 1024x768 (+4096), 24 bits
Mode 0x0312: 640x480 (+2560), 24 bits
Mode 0x0314: 800x600 (+1600), 16 bits
Mode 0x0315: 800x600 (+3200), 24 bits
Mode 0x0301: 640x480 (+640), 8 bits
Mode 0x0303: 800x600 (+832), 8 bits
Mode 0x0311: 640x480 (+1280), 16 bits
Config Status: cfg=new, avail=yes, need=no, active=unknown
athosbr99@athosbr99-Aspire-5732Z:~$