A strange printing behavior

[TimStone]

I'm looking for ideas based on some users experiences. Here is the problem:

An invoice print routine uses the same print function to print an invoice, counter sale, or estimate.
The only difference is in a few titles that are printed, and the customer info
This routine works EVERYWHERE except with one client where it used to work.
The client installed a new printer.
The customer can print invoices or estimates and it works perfectly
The customer can no longer print counter sales.
The problem cannot be replicated at any other client or in house.
When he put the old printer back on line, it now cannot print counter sales.
Again the same function is used to print all 3. The type selected makes a difference only in limited data output from the function.

So here is what I'm asking. I know it is not a FWH issue ( it has worked fine for many many years ). However, with all of your experiences with outputting to the windows print system, can anyone think of any reason this could occur ? Is there someting that tPrinter might expect the print system to respond that I could check, or any special characters that might prevent it from outputting ? I'm at a loss.

Thanks for your ideas.