Hi, we would definitely recommend upgrading to 2.5.236. NEWT should be alerting you to the new version, but if there's a filter/proxy blocking it, you'll need to download it from our website and install it over top. This won't change this error, but may fix other issues.
This sounds like more of a Windows networking issue than a NEWT issue, but we're glad to help where we can. Could you confirm this by trying to visit that server from Windows itself and let us know if you get a similar error? You can either use "\\ServerName" or the IP "\\172.16.200.144".