[exim] Problems with Exim 4.66/SA 3.1.8 Disconnects

I am still having problems with the following errors popping up from time to
time:

******************
An error was detected while processing a file of BSMTP input.
The error message was:

421 Lost incoming connection

The SMTP transaction started in line 0.
The error was detected in line 3.
0 previous messages were successfully processed.
The rest of the batch was abandoned.
421 Lost incoming connection
Transaction started in line 0
Error detected in line 3
******************

I googled the problem and setup a socket for SA to talk to Exim, removed the
bayes autolearn, limited the checks to emails less than 100k, deleted the
bayes token & autolearn files so they would be reasonable in size,
everything I could think of to try to eliminate the problem, and now it's
started popping up again.

I seriously doubt it's a CPU/Memory/Disk issue... The machine is an Athlon
64 X2 5200+ with 4 GB ram, and a drive array that benchmarks out at
78MB/second throughput... The machine regularly runs at <.2 load.

Anyone have any clues as to what is going on here, or if this is a known
problem being fixed on either side? I saw references to earlier versions of
SA and Exim not having this problem, so it seems to be something recently
introduced.