Macbook External Display no Signal
Here are some troubleshooting steps that I would try:
Reset the System
Reset your Mac's parameter RAM and SMC
Try another Cable
Although you are using the official MiniDVI to VGA adapter, it is possible that it might be damaged, so I would try connecting your monitor with another official adapter.
Reset the Resolution

Start up in Safe Mode (Power + Shift on startup)
Apple Menu =&gt; System Preferences
Choose Displays from the Views menu.
Select another resolution and refresh rate.
Restart.

Software Update
It is also possible that you need to update to Lion (Maybe even Mountain Lion if you want).
Other Links and Resources
Another Apple user who was using a Powerbook with the Acer x163W had issues too. That question was answered here and recommends a different monitor because of the Acer monitor's lower resolution than his Mac.