Hi Mick Head
I think to test psprint.drv I would:-
1] Follow the steps in the psprint readme file in order to add the printer PPD file to the psprint.drv
2] Create a new OS/2 printer object, name the printer, select to install a new driver, enter the path to the psprint.drv file and click Refresh, select the printer from the displayed list.
3] Open the Properties of the new OS/2 printer and setup output port and Default job properties.
4] Try to print the document that fails to print with the other printer.
If the above fails with the same error I think I would then contact the author of psprint.drv, Alex Taylor, and ask if there was any chance he could look into the problem.