[maddog]

I was having problems because somehow my preferences indicated mirroring on.
Since I am running 10.6.3 the old mirror friendly extensions do not work properly, I found myself in a lose lose situation.
Looking for a solution in the web I found an applescript that solves the problem. The original script is not good, a minor alteration makes it work fine
Here is the link for the original script:
How to disable Mirror Displays! - InsanelyMac Forum

Now because the screen scrambles you can not use that script above. A minor change and it works.
here is the modification

tell application "System Preferences"

activate
delay 15
reveal anchor "displaysArrangementTab" of pane id "com.apple.preference.displays"

end tell
tell application "System Events"

tell application process "System Preferences"

tell window 1

tell group 1 of tab group 1 to click checkbox "Mirror Displays"

end tell

end tell

end tell


How to make it work. Prepare everything but do not connect the external monitor (which should be on)
When everything is ready run the Applescript above.
Now you have 15 seconds to connect the external monitor to your mini.
Wait.
If you did everything right you will get the mirror off and the two displays will came back visible.
If 15 seconds is not enough change the 15 in the script by as many seconds as you think you will need.
Once the script is running just wait.
Again, if everything was done correctly both screens will come back live.