This indicates the CBR interface card's receive buffer filled and overflowed for longer than the TA-NWT-001248 threshold, meaning incoming CBR cells arrived faster than the card could drain them. An admin seeing error(2) here on a leased-line-emulation circuit knows they are losing data to a downstream bottleneck rather than an isolated glitch, and should check the far-end clock source or the card's egress path. For example, a mismatched clock source between two CBR endpoints could cause this to fire repeatedly, degrading a DS1 circuit's TDM data with periodic overflow errors.