Office to office calls over SIP trunks on CS1ks using 6 digit CDP. Call leaves A over SIP and arrives at B over SIP. If called DN is cfxa to home, cell or wherever, original caller will hear intercept or fast busy. Nortel and NetVersant engaged on problem for 30 + days with no resolution. Have looked at patches, NCOS levels, FRLs, and captured dozens of enhanced traces with no resolution. Any ideas appreciated.