jgroups related:sender not found in xmit_table

i am getting following error messages in our environment,

19 Jan 2012 21:58:32.194 ERROR [NAKACK] sender 10.32.4.44:44691 not found in xmit_table
19 Jan 2012 21:58:32.199 ERROR [NAKACK] range is null
19 Jan 2012 21:58:32.204 ERROR [NAKACK] sender 10.32.4.44:40483 not found in xmit_table
19 Jan 2012 21:58:32.208 ERROR [NAKACK] range is null
19 Jan 2012 21:58:32.224 INFO [RPCManagerImpl] Received new cluster view: [10.32.4.52:34977|11217] [10.32.4.52:34977, 10.32.4.51:43712, 10.32.4.44:55860, 10.32.4.44:44087, 10.32.4.44:40135, 10.32.4.44:37605, 10.32.4.44:44691, 10.32.4.44:40483, 10.32.4.44:34139, 10.32.4.44:32887, 10.32.4.44:47907, 10.32.4.44:40620, 10.32.4.44:53761, 10.32.4.44:60928, 10.32.4.44:52758, 10.32.4.44:49354, 10.32.4.44:40842, 10.32.4.44:44159, 10.32.4.44:47196,

Please clarify my questions,

1.when and why these error messages occur?

2.why each server in a cluster showing different multicast ports?

3.Are these eror message cause any functionality?

please clarify my questions..

Thanks,