There is like 50 different models of Acer Aspire LT. See if you can find your
model and there is times how to config your WIFI..
https://wiki.ubuntu.com/LaptopTestingTeam/Acer?highlight=%28acer%29
Follow the Dapper guide lines at this link
https://help.ubuntu.com/community/WifiDocs/Device/DWL-G122_%28Rev_B%29