ava.net.ConnectException: Connection refused

While doing test found that few times get message "Connection refused".

When we get this message some times I loose thread and run stops. Some times I see this message but soapui keeps running. Normally run using loadtestrunner.sh script.

Tried chagning TIMEOUT values but that do not have impact on this error. Tried applying latest patch for Apache but that did not change anything too.
Do not see any error message in server log.

Need Help:
What can cause "Socket exception : Connection refused"?
What I can monitor or fix to overcome this issue?

Thanks a lot for help.

Actual Error in SoapUI:18:43:31,764 INFO  [WsdlRequestCredentialsProvider] 155.90.82.7:8080 requires authentication with the realm 'OM'
18:43:31,766 DEBUG [SoapUIMultiThreadedHttpConnectionManager] Freeing connection, hostConfig=HostConfiguration[host=http://155.90.82.7:8080]
18:43:31,766 DEBUG [SoapUIMultiThreadedHttpConnectionManager] Notifying no-one, there are no waiting threads
18:43:31,767 ERROR [WsdlSubmit] Exception in request: java.net.ConnectException: Connection refused
18:43:31,767 ERROR [SoapUI] An error occured [Connection refused], see error log for details
java.net.ConnectException: Connection refused
        at java.net.PlainSocketImpl.socketConnect(Native Method)
        at java.net.PlainSocketImpl.doConnect(Unknown Source)
        at java.net.PlainSocketImpl.connectToAddress(Unknown Source)
        at java.net.PlainSocketImpl.connect(Unknown Source)
        at java.net.SocksSocketImpl.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at java.net.Socket.connect(Unknown Source)
        at java.net.Socket.(Unknown Source)
        at java.net.Socket.(Unknown Source)