help with custom board based on mpc5200b

Hello, we're using a custom board based on mpc5200b

We are using kernel 2.6.33 and when we using ethernet, we get 80% packet =
loss with ping.
Where could i find the solutions?

U-boot information:
CPU:   MPC5200B v2.2, Core v1.4 at 132 MHz
       Bus 132 MHz, IPB 132 MHz, PCI 66 MHz
Board: Ran Controller Board

I2C:   85 kHz, ready

Thanks

Lorenzo=