John,
I am going to assume that you either have SIP or some sort of ISDN trunking [T1/E1/BRI/PRI]. If that is the case and you are using Call Routing Tables then make sure that you don't have a rule that blocks No Caller ID.
E is typically used for Empty or No DID received, but if you are looking at Outside Party Number as your Key instead of Trunk Number then the E means no Call ID and will route according to that or you could just have a blank entry that means nothing as well.
Hope that helps,
TE