iMac as a server interrupting router?

I'm using an iMac (leopard 10.5.3) as a server at my office in order to share files. Everyone connects to a partition of my hard-drive at mycompname.local and it works great compared to their past system of passing around flash drives. There are 5 computers using the router (linksys wrt54g).

However, since we have started this, the router has been dropping out constantly. It is not our isp. The signal drops down to 3 bars and no internet comes through. It always comes back but only after about 15 minutes of power cycling the router. Has anyone ever had a similar problem? Is this something I can somehow fix, or does this just sound like a dead router? Is there a different router that we should have that might be more powerful or reliable?

Thanks,
Ryan