Error Messages (LCD, PC) or LED Lights - Troubleshooting

Error Message on LCD

• LOAD LETTER is displayed on the printer LCD. What does it mean?
• "DX" is displayed on the LCD, but what does it mean?
• "MX" is displayed on the LCD. What does it mean?
• I see the message "SIZE MISMATCH" on the printer LCD. What does it mean?
• I see the message "SIZE ERROR XXX" on the printer LCD. What does it mean?
• I see the message "DX LEVER ERROR" on the printer LCD. What does it mean?
• I see the message "DOWNLOAD FULL or FONT FULL or MEMORY FULL or IGNORE DATA" on the printer LCD. What does it mean? 
• "MP tray" is displayed on the LCD. What does it mean?
• I see the message "PAPER JAM" on the printer LCD but I cannnot see any jammed paper. What should I do?
• Why does the LCD of my machine display "CHANGE DRUM SOON"?
• "JAM C" error appears on the LCD. What should I do?

LED Indication

• What do the LED indications mean?

Error Message on PC Display

• When installing the Macintosh OS X printer driver it displays a message that you need to type your password to install this software.
• The message "xxxxxxx.xxx can't be opened because it is from an unidentified developer." appears on OS X v10.8.x. (where xxxxxxx.xxx is the file name.)
• The error message "Invalid format for short nick name" appears when printing a document. (Mac OS® X 10.5 or greater)
• I'm using Windows® 8. I insert the CD-ROM supplied with my machine into my PC's CD-ROM drive, but the error message "This CD does not contain drivers for your computer operating system." appears.
• I'm using Windows® 7. I insert the CD-ROM supplied with my machine into my PC's CD-ROM drive, but　the error message "This CD does not contain drivers for your computer operating system." appears.
• I receive an error message stating "USB Device Not Recognized. One of the USB devices attached to this computer has malfunctioned, and Windows does not recognize it" when I connect the Brother machine to a computer.
• The printer cannnot print and the error message "There was an error writing to LPT1:(or BRUSB) for the printer." appears on my PC. What should I do?
• I'm using Windows® XP SP2 or Windows Server 2003. An error message referring to BRSVC01A.EXE appears after installing the printer driver and I cannot print. What should I do?
• The error message "Can not load Word for Windows 6.0 files" appears at the end of the software installation. I have installed Windows® XP Service Pack 2 (SP2). What should I do?
• I am using Windows® 2000 or XP and I get the following error message on the PC: Spoolsv.exe or Spooler Subsystem app has encountered a problem and needs to close. How do I clear this error?
• I receive an error message when trying to use network functions.(For Windows®)
• My Antivirus Software gives a warning message during the installation of Web BRAdmin.