[ubuntu-uk] some user losing internet access

[M Castle]

Hello all,

My quest to spread the ubuntu word has brought me to a problem. I have set up 
feisty machines and introduced them to cafe's to remove their windows 
dependence and provide them with a stable system to stream music and do their 
paperwork/email etc.

Over the last few weeks though, two of these machines have symptoms of a 
problem. users are losing their internet connections and their music is 
grinding to a halt.

The wireless seems to be fine, so the connection is still there, and the admin 
account (not root, but admin) seems to keep the connection after the user 
accounts have lost theirs.

after 10-20 minutes it will reconnect automatically.

I'm runnning feisty on a dell  optiplex320.
512Mb
Pentium Duo 3.0GHz

can anyone offer any suggestions?