[SunHELP] HSI Card problem

[Philips Anwin-Q16166]

Hi all,
 I am having an E3500 server connected to x25 network via HSI cards. There are two HSI cards and 2 ports on each cards are connected to 3 routers. The problem is the some ports on the HSI cards are down. After a reboot sometimes even the faulty ports come up. 

We had tried replacing the HSI cards many times and now we feel that it cannot be a hardware problem.

We had tried giving loopback tests on HSI ports using hsi_loop command. For the faulty ports, software loop works while hardware loopback fails. 

What could be the problem? Can someone help me out?

Regds
Anwin Philip