OSPF: Socket error: Operation not permitted

[Przemyslaw Zoltowski]

hello,

i'm looking for help with ospf protocol on birdc. i'm using bird in 
production environment for more then 3 months.

0001 BIRD 1.3.4 ready on

FreeBSD mp-r2 9.0-RELEASE-p3 FreeBSD 9.0-RELEASE-p3 #0: Tue Jun 12 
02:52:29 UTC 2012 amd64

i get following errors in bird.log:
08-02-2013 20:13:06 <ERR> OSPF: Socket error: Operation not permitted

sessions with my neighbours are going down, and after aprox 10 minutes 
everything gets working without any reboot of router nor daemon.

what can cause such problem ?

greetings
pz