Never ending i-framp in polymix-4

I've built a new Polygraph environment this week, running Polygraph 
version 2.8.1 on two Fedora Core 1 Linux boxes.  Everything built and 
installed without trouble, and everything runs without errors, including 
generation of IPs and generation of the DNS zone files.  (Hooray!  I 
remembered it being harder a couple of years ago when I setup my last 
polygraph pair.)

I was able to run simple.pg locally and across tes boxes and a 
datacomm-1.pg with the proxy in the loop.  All of them worked without 
trouble.

However, when I run polymix-4.pg, it seems to get stuck in the "i-framp" 
fill phase.  I've specified "size ProxyCacheSize = 10GB;", and so I 
expected it to stop at 20GB and move into the next phase, but the last 
status printout five hours into the run shows fill.size at 34.70GB and 
still growing:

295.21| resource usage:
         CPU Usage: 3.28hour sys + 30.95min user = 3.80hour
         Page faults with physical i/o: 692

295.21| fyi: phase progress:
         duration:        4.92hour goal: 20.00min (1475.03% complete)
         xact.count:      4712964
         fill.size:       34.70GB
         xact.errs.count: 0
         xact.errs.ratio: 0.00
         WSS frozen

295.21| fyi: min 'direct' objects in working set:
         global public: 510641 (~5.17GB size, 569/609=93.43% frozen slices)
         local private: 169626 (~1.72GB size, 391472/391472=100.00% 
frozen slices)

WSS froze about three hours ago at 5.27GB, and fill.size crossed 20 GB 
soon after.  I'm using the polymix-4.pg that shipped with this version 
of polygraph, so it has the updates for robot interests discussed here, 
so I guess is isn't a known phase sync issue: 
http://www.web-polygraph.org/downloads/upgrade2p8p0.html

The only changes I've made to the workload are the IPs of my test 
machines, the fill rate, the resolvers, and the fill rate.

What else am I missing?

Thanks!