VBA crashing excel inconsistently

[S Oberlander]

I have a userform macro stored in two different workbooks (personal and public);
When I ran it from the personal workbook it crashed excel, from the public workbook it worked fine.
The. Exact. Same. Macro.
I tried deleting the module from the personal workbook and copying it from the public one, now it works again.
(FYI it was built by me in the personal workbook)

Why would this happen?

Note this macro is about 2 years old and gets used regularly and then today... Bam! it doesn't go...

 

[ranman256]

do you have mixed bit systems? : 32 bit Win OS, and 64bit Excel? or vice versa?
we had problems with this.

 

[S Oberlander]

no everything is 64bit