Using DellPowerConnect POE switch and Cisco 7960?

I have install an asterisk server in a small business environment.

The phones are configured to the server and can call out and receive calls fine, but about every 3-4 minutes (it seems) the data network goes down.

We have pinged the server and the switch, the server stays up, but the connection to the switch goes down intermitantly. The connection is fine 95% of the time, but loses for about 4-6 seconds and then returns.

The really odd part is, the connection is only lost for the computer connected through the phone to the network. I am wondering if the Cisco Phones are tempermental with the switch we have just purchased.

Here is the hardware.

Cisco 7960 Phones
Dell Power Connect 3448P POE switch.

Has anyone out there used this hardware combination successfully (or unsuccessfuly?