Network Shares become Unavailable

I’m running into an issue where one of my servers’ network shares become unavailable after a few days. The only fix I’ve been able to do is to reboot it. They’ll be available after that, but only for a few days (week max) and then they’re unavailable again.

The server is running Server 2003 SP2. It’s got plenty of HDD space and 3GB of RAM.

It’s running as an application server, hosting 3 programs that have databases running SQL2005 Standard. We keep them on the same server because they integrate with each other automatically.

What would cause this issue to be happening?