Neighbor lost for bird6

Hi all, I'm facing a weird problem: we run BIRD with identical configuration on 2 different servers, both connected on the same peering lan. We had "Error: Neighbor lost" error message for all the IPv6 bgp speakers, on both machines, while the v4 deamon had no problems. Issuing a "kill -s HUP" didn't change anything, while shutting the deamon down and then re-starting it actually solved the problem. From the logfile I see that all the speakers went to "flush" state, then "stop", and then "start", but none of the sessions came up. Any clue on what could be the cause? TIA, Simone. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.