Customised Ribbon periodically wont run macros

[JeffGrant]

Hi All,

I have this niggly little issue which is somewhat annoying.

I have a custom group which is on the customised tool bar.... no problem.

The Start Macro, launches a User form... no problem.
The Automatic and Manual icons are just to turn on and off the Calculation as found in the Formulas Group.

However, at least twice a week, for reasons I do not understand, clicking on the Start icon, gives me the deadly..... "Cannot run the macro" error message.

All this macro does is this

Sub Start()
    Welcome.Show vbModeless ' show welcome screen
    Application.Wait Now + TimeValue("0:0:03") 'screen needs to catch up
End Sub

to fix it, I customise the ribbon, delete the start icon and then add it again, then off we go.

Clearly, it is something in my code that Excel does not like, or that I have not done, I just don't know what.

All suggestion are gratefully received.

Thanks