First off, the IP network you use looks fishy: the "usual" setup is to have a private network and routing to the internet shut off. Then, via a proxy server in a DMZ, selected systems are allowed to access the internet. To hide the (not-routable) private addresses from the internet usually NAT is used.
This works because several addresses of the IP address range are set aside and defined as a) not being routable and b) used for private purposes. This means, the normal property of an IP address to be distinct worldwide is not the case with these addresses. Everybody can use them (instead of having to registering them with the IANA), but in return you cannot access the internet with these.
The address ranges in question are (see
RFC 1597 or
RFC 1918, "Address Allocation for Private Internets"):
10 (-> one class-A net)
172.16 - 172.31 (-> 16 class-B nets)
192.168.0 - 192.168.255 (-> 256 class-C nets)
I presume you (metaphorical - maybe your predecessor admin) wanted to set up a private network, but mixed up addresses. Right now you are using official internet addresses, probably without having them registered and them being duplicate. This works well as long as there is absolutely no connection to the internet, but once there is (and you say that there is now) this will lead to errors galore.
I still cannot tell you why your specific error message showed up, but i suggest that you correct the most obvious error first, which will definitely prevent successful operation anyway.
I hope this helps.
bakunin