[squid-users] empty core files

[Rhino]

Running squid-2.7.STABLE1-20080528 on Debian linux  2.6.19.7 kernel 
using wccp2 and iptables for transparency.
Put into production approx. 2 weeks ago, approx. 10k customers are 
browsing transparently without any complaints of latency, and we're 
seeing a measurable incoming bandwidth savings on our ISP links - so 
things seem to be performing well.  However I've discovered a number of 
completely empty core files in my squid logs directory.  Some are as 
little as 3 minutes apart.  Could an exploited vulnerability be 
generating these?
Appreciate the help.
-Ryan