A whole bunch of fairly important issues caused by Office 2003 SP3:
The AutoCorrect feature does not work in Outlook 2003 after you install Office 2003 SP3
The Fast Saves feature in Word 2003 no longer functions after you install Office 2003 Service Pack 3
You receive an error message when you try to open a file or to save a file after you install Office 2003 Service Pack 3
You are unexpectedly offered Office 2003 Service Pack 3 when you use Microsoft Update, Office Update, or Automatic Updates
Error message when you try to install an Access 2003 add-in for all users by using the Add-In Manager on a Windows Vista-based computer: "There was an error adding to the registry"
You cannot open Microsoft Excel 5.0/95 Workbook files that contain Visual Basic for Applications macros in Excel 2003 after you install Office 2003 Service Pack 3
You may experience issues when you run the Microsoft Office Document Imaging program after you install Office 2003 Service Pack 3