A couple of possible solutions I posted recently both involved setting
the workbook to manual calculation. Full details can be found at
thread. (Search on "Workbook Open event does not fire".)

Peter T wrote:
Hi Jack

I've also had the same problem intermittently. We are by no means
alone as a
quick Google will reveal. But I have not seen cause/solution posted.

"Shift" has been mentioned but don't rule it out completely as a
possibilty,
it can be the mysterious route of several unexplained problems and
not at
all obvious.

I've not had a problem recently but I can't be totally confident of
Workbook_open. To the extent I now have a backup check in Auto_Open.
My open
routine needs, amongst other things, to set a global variable. All
"should"
be have been triggered from wb_open but I also have:

Auto_Open()
If myGlobalVar = 0 then Do_Open_Routine
'Do_Open_Routine is in a normal module
'that should have been done already

May seem like overkill but it's not much extra, just to be sure!

Regards,
Peter