Macros hanging up on end sub commands

I have a collection of VBA macros which have been working without problems for years on a range of computers and Excel versions.
I am now in a new location on a new PC but using Standard Excel 2010 package.

Some (but not all or even most) of these macros, which call and run sub routines as normal are now hanging up on the end sub command, instead of returning control to the sub routine that called them.
This only happens on some of the sub routines, not all.

Any suggestions for what may be causing this??

I guess it might help if you shared some of the code that is giving you a problem.