excel 2007 vb6 application not running on Excel 2010

[switters_aka]

Here is my problem. I have created several VBA applications in Excel and distributed them extensively to end users some of whom are using Excel 2010. In some cases the app runs perfectly but in one case it the same application was sent to two users the second of whom then sent the same application to the first user. The first user who got the application directly from me could run it successfully but when he received the 'same' application from user2 it wouldn't run. The only thing user 2 did was save the file with a different name and the code does not depend on the file name. The file extension was till .xlsm.

If the app simply didn't run on Excel 2010 because it uses VB7 then I would know where to start but what makes this problem doubly frustrating is the fact that it sometimes works and sometimes doesn't. Can anyone enlighten me as to what the problem is and how to go about dealing with it?

Thanks in advance.

 

[diddi]

check the references. VBE>Tools>References
and see if any are MISSING: ....
save as will apply the references on the other puta to the document and then it will fail on machine 1