If You don't want to go to the link here's a short summary:
Using an external screen to display an extended desktop or clone the content on the internal screen does not work.
The Display-utility found under System > Preferences can correctly identify the attached screen, but is not able to activate it.
It behaves as if the external screen is working normally (cloning, extended desktop) but the external screen remains in power save mode or at least not reacting at all.
The only way to activate it is to reboot the unit with the external screen attached from start. Then all functions supported by the display applet works as expected.
I can even unplug the ext screen, plug it in again and all is still working as expected.
I was convinced that this was an Intel specific issue, but it seems not. I have tested 2 nVidia units with the Beta of F12 showing exactly the same problem as I have seen on the Intel units.
Additional - maybe somewhat redundant info: even Ubuntu 9.10 with the latest nVidia proprietary driver shows the same problem.
So, it seems I am a bit incorrect in the problem description in the filed bug mentioned above, since the bug is actual only on the Toshiba's that have a Toshiba BIOS.
Toshiba's with Phoenix / AMI BIOS'es do not show this issue.
Anyway, this problem was introduced in F11 and has been lurking there since.
It seems that there is little attention to this bug - is there any other Toshiba-BIOS-unit-user with similar experience or maybe some nice workarounds?