[cisco-voip] Troubleshooting ISDN PRI alternating between TEI_ASSIGNED and AWAITING_ESTABLISHMENT

[Robert Kulagowski]

2851 router running 12.4.10a.  ISDN PRI not coming up; sh isdn
stat shows alternating between TEI_ASSIGNED and AWAITING_ESTABLISHMENT.

isdn q.921 debugging shows
EVENT: Pri_Activate_L2: sending NL_EST_REQ
L2_EstablishedDataLink: sending SABME
user TX -> SABMEp sapi=0 tei=0
user TX -> SABMEp sapi=0 tei=0
user TX -> SABMEp sapi=0 tei=0
user TX -> SABMEp sapi=0 tei=0
EVENT: CCPRI_Go: received NL_EST_REQ

Since this happened all of a sudden, I'm assuming that it's the
carrier, but I'm not sure what exactly to tell them, since it's
unlikely they understand Cisco terminology.  Can someone translate this 
into telco-ese?