The D6640 or D6641 line card on the D6600 Receiver is occassionally resetting itself. All of the lights turn red for a few moments, then go off and the line card returns to normal.
The line card is performing this as a precaution. If selected in programming, the line card will refresh itself after a certain number of calls providing incomplete messages to the receiver. By resetting itself, the receiver is making sure that the configuration in the line card is correct and working properly, and that the line card is not the cause of the corrupt data. The area of programming to set this is in the CPU configuration (2.2.31), Line Card Refresh. If this feature needs to be turned off, it can be set to 0.