Best way I know how to do this is with a macro. A simple one to do
what you want would be:

Option Explicit
Dim Counter As Integer
Dim StartSheet As String

Sub Unfreeze()
' First find where we're starting from
StartSheet = ActiveSheet.Name

' Step through sheets and unfreeze
For Counter = 1 To Worksheets.Count
Worksheets(Counter).Activate
ActiveWindow.FreezePanes = False
Next Counter

' Go back to the start point
Sheets(StartSheet).Activate
End Sub