Jimgoode,
That error message indicates the problem most likely is with the PC, not SME.
I had a similar problem (many years ago working with NT) and I think the problem was caused by a faulty N/W setting on the PC. The default gateway was set to 192.168.11.1 instead of 192.168.1.1 or something similar.
Check these settings carefully - compare the settings with one of the PCs that can communicate with SME. it may be the cause of your problem.
As a quick check, can you successfully PING SME or one of the other PCs?
Cheers
Ian