LinuxQuestions.org - "No signal" on external monitor

have toshiba tecra a11-11q. after hotplugging external monitor through vga, i have no signal message on that screen. xrandr:

Code:

Screen 0: minimum 320 x 200, current 2646 x 1024, maximum 8192 x 8192

VGA1 connected 1280x1024+1366+0 (normal left inverted right x axis y axis) 338mm x 270mm

  1280x1024      60.0*+  75.0  

  1280x960      75.0  

  1152x864      75.0  

  1024x768      75.1    70.1    60.0  

  832x624        74.6  

  800x600        72.2    75.0    60.3    56.2  

  640x480        72.8    75.0    66.7    60.0  

  720x400        70.1  

LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm

  1366x768      60.2*+

  1024x768      85.0    75.0    70.1    60.0  

  832x624        74.6  

  800x600        85.1    72.2    75.0    60.3    56.2  

  640x480        85.0    72.8    75.0    59.9  

  720x400        85.0  

  640x400        85.1  

  640x350        85.1

here everything seems to be fine. krandrtray also shows that external monitor is operative.

after rebooting computer both monitors work, but i can't change brightness on lvds.
i'm running archlinux, but the same results were on fedora, ubuntu and mint. there is no such problem on windows xp.
maybe it is not supported yet for Core Processor Integrated Graphics, but i couldn't find such information.