[Serusers] Weird Error Message

Today we tried to install a Grandstream phone at a cutomer site but were unable to make it work. We have about 40 of these phones (all configured by US in the exact same way) and all working fine. But upon plugging this phone, SER started generating this message constantly in the log file: Nov 13 16:53:14 maui /usr/local/sbin/ser[5066]: ERROR: udp_rcv_loop:recvfrom:[11] Resource temporarily unavailable Nov 13 16:53:16 maui /usr/local/sbin/ser[5068]: ERROR: udp_rcv_loop:recvfrom:[11] Resource temporarily unavailable Nov 13 16:53:19 maui /usr/local/sbin/ser[5065]: ERROR: udp_rcv_loop:recvfrom:[11] Resource temporarily unavailable Looks like every time a REGISTER came in, that ERROR message would appear in the log file. All other Grandstream phones continued to register just fine. An ETHEREAL does not show anything that is obviously wrong with the message. I did restart SER but the message continued. Can anybody tell me what could be the cause of this error? Or if anybody wants to look at the ETHEREAL trace I can sent it directly (its about 1MB). SER Version is 8.11 Thanks, Andres