SOMETIMES, its caused because Excel is confused on the datatype of the column.
Before I import, I had to run a macro on my XL file to remove this confusion by turning the entire column as text. (single quote at front of text)
This is for fields that have both strings and numbers.
It then imported perfectly.
Code:
'put cursor in column to convert, then run this macro
Sub Cvt2Txt()
Dim iOff As Long
iOff = acivecell.Column - 1
While ActiveCell.Offset(0, -iOff).Value <> "" 'as long as the 1st col has data,...
If Left(ActiveCell.Value, 1) <> "'" Then ActiveCell.Value = "'" & ActiveCell.Value
ActiveCell.Offset(1, 0).Select 'next row
Wend
End Sub