I've been having OS X issues lately, so I've spent time in the Console (yes, the days of full function OSs are limited).
I liked this particular message:
2/28/10 10:32:19 AM [0x0-0x294294].com.microsoft.Excel Sun Feb 28 10:32:19 Stanford-MacBook-2.local Microsoft Excel
: The function `CGPDFDocumentGetMediaBox' is obsolete and will be removed in an upcoming update. Unfortunately, this application, or a library it uses, is using this obsolete function, and is thereby contributing to an overall degradation of system performance. Please use `CGPDFPageGetBoxRect' instead.