Home Network problem

For some reason, a home network which was working relatively well has stopped, and I can’t figure out why. I am connected through a Linksys Wireless G router. I can access the internet on my laptop, so I know the connections are good. But for some reason I can’t access the shared files between computers. This is a new problem, as I was previously able to do so. How can I troubleshoot the issue and find the problem?