Switch loop suggestion - Cisco Router

Hello Experts,

We used to have the following setup in a "cascade" setup.
3comA-connects to 3comB- 3comC connects to 3comD to 3comE and so fort. Total 7 Switches.

We bought a Cisco 2960 and decided to have all the switches connect to the Cisco as the
"Backbone Switch".

So we broke the "cascade" and now every switch connects to a different port on the Cisco 2960.

We are getting a loop after  this setup, every now and then different parts of the network loose connectivity.  We only have Vlan1 enabled and the default setup that came with the Cisco Switch.

To avoid any other switch from becoming a "root bridge", I ran the following command on the Cisco Switch so that it could be the main router:  
spanning-tree vlan 1-4094 priority 0.   (This did not work)

Any ideas on how I can find the loop?

Thanks,
R