Caller ID (CID) External Lookup - Problem BT


We have a little ASPX script that does caller ID against our backend systems (SQL databases).

The script itself works and when configured with Asterisk VOIP server to do lookups on incoming numbers it appears to work with everything except for BT landlines (well everything we have tested so far) … when a BT landline calls it just drops the call.

Turning the external caller id lookup off in asterisk and then calling again from the same BT landline works.

Anyone have any ideas?