If you receive this error while opening Excel or other Microsoft Office programs, it is usually caused by an Adobe PDF addon that is having problems. According to Microsoft, this can happen if:
1. The Microsoft Office Startup folder or the Microsoft Excel Startup folder contains either or both of the following Adobe Acrobat PDFMaker add-in template files:
2. Norton AntiVirus software is installed.
To fix it, delete the files from the startup Office folder. There are a few locations it might be, in my case it was in C:\Program Files\Microsoft Office\Office12\XLSTART. See this Microsoft KB Article on fixing the error.