Are you using the same Workbench setup on each? If so that is probably the issue.
Maybe it would be worth downloading one of the current ClassicWB versions and setting it up as a fresh install, adding your key to the S directory and seeing if Bloodwych (included by default with ClassicWB) will run. If that works then add and try a couple of other games. That will prove if it is something specific to your existing setups.