Why serial interface is often down?

[wei.xiong]

Cisco7206 with three PA-MC-8TE1+,and remote site is Cisco3745 with VWIC-2MFT-G703.After a few hours,some serial interface of different PA-MC-8TE1+ change down.Several interface is down and line protocal is also down.Several interface is up and line protocal is down.When I put the line into other interface or reload the router,it is OK.

Is it a hardware problem?

Thanks

[contactyk]

Probabaly YES....

[neclink]

if you could afford to test, I would recommend to populate all the cards with loopback plugs, clear the counters and let it run for a while. It will tell you. I could possibly be a IOS oany other issue.