modem disconnects

I have Vista Ultimate desktop.
Laptop XP Pro.

I have the laptop connected wireless and I can open browser and browse the
web hours and hours.

I am sharing a printer with the desktop and can usually print once from
the laptop.

But if I try to print again the modem disconnects from the network. I
have to shutdown the desktop and then reset them modem before I can get
reconnected.

Is there any fix for this?