Can't access macros in personal.xlsb workbook from macros in a second workbook

I can only access macros in my personal.xlsb workbook from other macros in the same workbook. When attempting to access these macros from a macro in a second workbook, I get the message "Compile Error - Sub or Function Not Defined." In the Project section of the VBA window, I can see and manipulate all macros in the personal.xlsb workbook and see and manipulate all macros in the second workbook. If I insert the modules that are in the personal.xlsb workbook into the second workbook, everything works OK. What am I missing?

My problem is occurring with only one instance of Excel open. Any ideas? Thanks

I ended up side-stepping the problem by placing the frequently used macros in an Excel Add-In file and referencing the add-in in the VBE references. Thanks for everybody's input.