I got smart serial error (mesa 5i25 w/7i76)

2 or 3 hours have passed after turnig on pc
my system got smart serial error. I attatched screenshot.
I don't know what this mean, why this happen and how to fix it...
please advice me

my system is
D525MW w/4g memory
5i25 & 7i76 installed
linux version: 10.04
linuxcnc version: 2.5.3

when I got those error messages just close alert window and check each axis motion it looks ok.
(I'm still setting up my system so I didn't have chance to manufacture something
now just press cursor key or page up/down key for checking motion..)

Those errors indicate that serial communication was interrupted somehow
The Break Error especially indicates something major wrong with communications.
this could be a bad cable connection, bad cards, or more likely a power supply issue.
Other possibilities are external noise induced by routing power cables near the 7I76/5I25 cable.

I would first check the 5V power at the 7I76 and field power at the 7I76 to make sure they are
within specifications.

I checked the 5v power at the 7i76 and field power at the 7i76 both are within normal range.
and I changed the cable till now no error message. but this error message is randomly appeared so need to watch for long time..
thanks a lot.