Excel freezes or "automation error: The object invoked has disconnected from its clients"

Hello,

In the attached file there is a userform with 4 commandbuttons . Each button calls the same module. However when pressing the buttons either excel crashes, or I get the message: "automation error: The object invoked has disconnected from its clients".

Sometimes one of the buttons will work, occasionally 2 or 3, so far never all 4. I'm not sure if its because of delays or an intermittent internet connection in my machine or for other reasons. Does any one have any suggestions to overcome this glitch? I'm using Excel 2010 and am a beginner VBA programmer.

Thanks so much,

Don