Wireless Networking works OK - Sometimes

OK - I understand many things about networking and wireless connections etc...but can't for the life of me figure out what's causing my problem.

What happens is - when I boot up the wireless connection makes the connection to the router with no problem. I can browse the internet using either IE8 or Firefox.

After a period of time - to be more precise a random period of time - the connection looks as though it's working but I will get a message informing me 'page unavailable' or connection manager pops up and informs me there is a problem with the connection. If I use the 'repair' function associated with the XP wireless icon on the task bar - it runs the process and then I can browse the net again. Obviously it's got something to do with flushing the DNS cache - what I am trying to discover is why does it fall over in the first place. I've had a look at various forums and tried several 'fixes' to the registry but nothing works.

Any hints on fixing this 'permanently' would be appreciated.

I wait in hope.