Information about this error was found in https://communities.vmware.com/thread/481316 , a thread about connecting to vCenter servers in combination with this error.
"The issue has been resolved. It was due to our vCenter server having a 512-bit SSL on it (was a previous upgrade from 4.0). "
In order to do that, java.security file should be modified. This file is located at c:\Program Files x86\Nimsoft\jre\jre7\lib\security\java.security, which is the JRE_Home for Nimsoft.
Changing value from 1024 to 512 in line "jdk.certpath.disabledAlgoritms=MD2, RSA keysize < 1024" resolved the issue.