Refreshing Pivot Table clears Values and Column Labels fields

When I attempt to refresh an Excel Pivot table (by right click .. Refresh), all of the Column Labels & Values fields disappear, leaving only Row Label fields and an empty Pivot Table. How can I keep Columns Labels and Values fields the same, avoiding the behaviour described above, and refresh only the data.

I've noted that this only seems to occur when I open a spreadsheet sent from another person, or if somebody opens up a spreadsheet I created with Pivot Table in it.

I'm using Excel 2007.

I solved this myself after much trial/error-

The source table had Column Labels formatted as Dates for columns. (11/1/12 to represent Nov/12, 12/1/12 to represent Dec/12, etc.). However the Pivot Table Values/Column Labels were 'Nov/12', 'Dec/12', etc.

Changing the column names in the Source Data to match those in the Pivot Table ('Nov/12) fixed this behaviour.