Only tested on Windows XP so far:
Goto LAN Properties and then goto IPX/SPX properties, then assign any non-zero “Internal Network number” in the given column.
The “Frame Type” can remain at the default “Autodetect” option.
However on each PC, a different non-zero “Internal Network number” under the IPX/SPX would have to be assigned.
The above definitely solved the problem of “Unable to join game” in Starcraft