Assuming 'on-line' means 'from my browser' (IE6,7,8, Firefox, Opera?) it seems more like a browser problem.
Things to try:
1. See if you can print to disk using the same printer driver.
2. See if you can print to disk using another printer driver.
3. Download one of those pdf-printers (like cutepdf or pdf995) and see if you can print to pdf.
4. Try the same from another browser.
5. Try your printer on another PC.
I have a Lexmark X1195 all-in-one which I have used for some time without problem. Out of the blue it just stopped printing on line. It will not even orint out emails yet any file can be printed without problem. I contacted Lexmark and they have been unable to solve the problem. Any ideas?