Combo Box Problem

I am having problems with a script that I put into Excel 2007 for a combo box that hides and unhides ranges based upon the selection of the combo box. Works 7 out 10 times. When it doesn't work, it put Excel into some kind of loop that requires that I shut it down and restart. The "VBA reset" button doesn't do anything. Once I restart, the script works again. What am I doing wrong?

Code:

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Private Sub ComboBox1_Change()
   
    Worksheets("Plan Sheet").Range("c7").Select
    Columns("D:UQ").Select
    Selection.EntireColumn.Hidden = True
   
    Range(ComboBox1.Value).Select
    Selection.EntireColumn.Hidden = False
   
    Worksheets("Plan Sheet").Range("c7").Activate
    Selection.End(xlToRight).Select
   
End Sub

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Welcome to DevX :WAVE:

Walk me through this....

1. You open the spreadsheet
2. You select something from the combobox
3. The code runs successfullly
4. ????? - what do you do next?