logical ip = not available; actions taken: Abort message

messaging gateway 10.0.1-2 on a VMWare appliance; some flavor of linux. 

Audit logs report that traffic received from just one IP is sometimes delivered normally and sometimes fails due to "logical ip = not available".  That ip and his domain are in the "good sender" lists.  There is no reverse DNS to that IP, but I'm not using RDNS within brightmail. 

Is there a fix within Brightmail or is this caused by something external to our site?

Thanks!

Mike