There was a similar discussion the other night regarding Acer Wireless connection.
Upshot of advice in that thread was to check which wireless card you have installed. If its the Intel(R)PRO/Wireless 2200BG network card look to see what version drivers it has. The latest one should be v.220.127.116.11.
I got some very good advice from Dipso. Shall go and look for the thread and find the link for you download latest drivers and give info about security problem.