I'm running Ubuntu 9.10 on Acer Timeline 4810G and I have installed ATI driver.

I tried to connect my 1680*1050 Samsung T220N as an external display. When I open System-Preferences-Display I see my external monitor, but I'm unable to set resolution higher than 1366*788, and when I click apply it asks me to logout and login again for settings to take effect. And my external display remains black.

When I used the intel adapter all worked OK.

I have the same problem with an Acer 4810TG and Ubuntu 9.10.

I'm using the latest proprietary Ati driver (9.12) and I get black screen when I'm trying to switch to the external screen. Sometimes it's able to do it but then it does not work when I try to go back to the laptop's screen. It's also strange that you are only allowed to do this in admin mode because it's writing in the xorg.conf. I don't think it should be writing anything in there. Also usually it writes something corrupt so X can't start up the next time I boot up my laptop.

This bug should be reported somewhere now that I know that other people also have this issue.