Hi,
1. Which operating system are you using?
2. Have you made any changes on the computer prior to this issue?
Download the driver using the following link: http://support.lexmark.com/index?locale=en&page=product&productCode=LEXMARK_X2250&segment=SUPPORT&userlocale=EN_US&frompage=null#2
If you are using Windows 7 computer then try installing Windows vista driver in compatibility mode.