After few minutes using, desktop and fonts in unity-menu goes blurry. See screenshot:

Closer image:

In all applications (browser etc.) graphics seem to be allright. After rebooting problem disappears for few minutes. Changing the wallpaper also makes the desktop clear (for a while) but fonts are still blurry.
I have ubuntu 12.04 and windows xp dualbooted.
lspci:
00:00.0 Host bridge: Intel Corporation 82945G/GZ/P/PL Memory Controller Hub (rev 02)
00:02.0 VGA compatible controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02)
00:02.1 Display controller: Intel Corporation 82945G/GZ Integrated Graphics Controller (rev 02)
lshw -c video:
*-display:0
description: VGA compatible controller
product: 82945G/GZ Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 02
width: 32 bits
clock: 33MHz
capabilities: vga_controller bus_master cap_list rom
configuration: driver=i915 latency=0
resources: irq:16 memory:d0100000-d017ffff ioport:30c0(size=8) memory:c0000000-cfffffff memory:d0180000-d01bffff
*-display:1 UNCLAIMED
description: Display controller
product: 82945G/GZ Integrated Graphics Controller
vendor: Intel Corporation
physical id: 2.1
bus info: pci@0000:00:02.1
version: 02
width: 32 bits
clock: 33MHz
capabilities: cap_list
configuration: latency=0
resources: memory:40000000-4007ffff
Have you got any ideas to get this solved? Thank you very much!