SA 3.01 eventually stops noticing DNSBLs

[Jay Levitt]

I have SA 3.01 running under mimedefang 2.43 with sendmail 8.13.1.  At 
some point, SA seems to stop doing lookups on the DNSBLs; spam gets 
through that is listed in multiple BLs; if I check manually with 
spamassassin -t, it detects the BL entry, even if I run it moments after 
the spam was received. 

I don't see anything obvious in the logs.  What can I do to troubleshoot 
this?

Jay Levitt