network locks up with udp traffic

[Dmitry Sivachenko]

Hello!

I am using FreeBSD-10/stable.  We have a program at work that transmits data via UDP.
When I run several instances of this program simultaneously, after a few seconds network stops working.
If I login from console, I see some network daemons like ntpd, snmpd are in "*udp" state.

If I try to deal with network interface (ifconfig igb0 for instance), ifconfig utility stuck in "L" state (Marks a process that is waiting to acquire a lock.).
I found the only way to fix that: reboot.

What can be the cause for such a behaviour?

Thanks.