I'm using CallManager 4.2(3)sr2b and ATA186 with SCCP firmware ATA030203SCCP051201A.
Everything else is ok (i can make calls or fax from ATA using both ports, i can ping the device using CCM and my laptop).
Thank you in advance for the help.
I noticed something similar when access the device via its web interface through a pix/asa where the MSS window was exceeded and the packet was dropped. Don't know if it applies to your scenario but thought I would at least mention it.