Does it work for any length of time when you plug in or does it freeze immediately?
Does the screen freeze or go blank?
Is anything being written to the event log that would suggest a duff driver (related to power management)?
I've heard of a couple of problems related to Toshiba laptops but not acer. One is to do with power management in that the processor runs faster on mains than it does on battery, the laptop overheats and freezes. This was a motherboard fault that was fixed under warranty. The other was loose mains connector that was flexing the motherboard and cause the LCD to switch to external monitor. Plugging a screen into the external XGA port it was found the laptop had not frozen after all.