meaning of 'event_wait : Interrupted system call'

I manage several OpenVPN links.

Sometimes while the VPN connection is UP for a few minutes/hours it suddenly gets down with the following (error) message:

event_wait : Interrupted system call (code=4)

Sep  8 11:13:46 hostname ovpn.udp[2622]: Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 2048 bit RSA
Sep  8 12:05:59 hostname ovpn.udp[2622]: event_wait : Interrupted system call (code=4)
Sep  8 12:05:59 hostname ovpn.udp[2622]: TCP/UDP: Closing socket

Dec 18 02:14:12 hostname ovpn.udp[5783]: Initialization Sequence Completed
Dec 18 02:15:43 hostname ovpn.udp[5783]: event_wait : Interrupted system call (code=4)

Restarting often solves the problem.

What does this message mean? What is triggering this error?

Thanks