Symptoms were the same as in another thread, although it was in regard to running a mixed cluster of 3.10 and 2.6.32 kernels, so I thought I would give the fix a try, and it worked. However, I'm not running a mixed-kernel cluster; everything is 3.10-4. Anyway, this worked and fixed the issue. But, WHY must this be done?
find /sys/devices/virtual/net -name 'multicast_snooping' -exec sh -c 'echo 0 > {}' \;
find /sys/devices/virtual/net -name 'multicast_querier' -exec sh -c 'echo 0 > {}' \;
service cman stop; service cman start; service pve-cluster restart