Can’t print from Outlook Express 5

My client was able to print her e-mail from Outlook Express 5 before, but can’t now. She claims she made no changes to her PC, and I find none either. A printer is attached locally (default), other network printers are also present, and all can be printed to from other applications.
When attempting to print by clicking the print icon an error message states: “Printer cannot be found.” If I click PRINT on the FILE menu I get the same message. No dialog box appears giving a choice of installed printers.
I have reinstalled OE5 over the existing installation, and got the same error. I suspect a corrupted .dll file.
Any ideas?