I upgraded to 126.96.36.199 and it does not solve the problem. My software has had this issue for many versions but I've just worked around it by ensuring the files are formatted correctly. It's only now becoming a problem.
I've attached two excel files, the one that works ok ("OK.xls") and one that does not ("Fails.xls"). Changing to .xlsx does not make any difference.
I won't include all of my code because it doesn't really serve any purpose, but a simplified version is:
Dim dateCell As Cell
Dim dateOptions As New FindOptions()
Dim dateArea As New CellArea()
dateArea.StartColumn = startColumn
dateArea.StartRow = HeaderRow
dateArea.EndColumn = maxColumn
dateArea.EndRow = HeaderRow
dateCell = sheet.Cells.Find("01/01/2010", Nothing, dateOptions)