PRI error!

Anyone have any suggestions to this PRI error… We just upgraded to the latest rev’s and now we are getting the below error. After getting them for awhile it drops all calls.

We are using NFAS on with 4 T1’s.

thanks

Jul 27 10:45:06 WARNING[28151]: chan_zap.c:8093 zt_pri_error: [Span 0 D-Channel 1] PRI: !! Got reject for frame 60, retransmitting frame 60 now, updating n_r!
Jul 27 10:45:06 WARNING[28151]: chan_zap.c:8093 zt_pri_error: [Span 0 D-Channel 1] PRI: !! Got reject for frame 60, retransmitting frame 61 now, updating n_r!