Pivot tables: disappearing data fields

[the1859]

I am working with a fairly large range, and I whenever I go to create a pivot
table some of the columns don't show up as fields. These are normally
columns somewhere in the middle, so it doesn't seem like it's a size
limitation problem. If anyone has any ideas, I'd really appreciate the help.
Thanks

 

[Mattlynn via OfficeKB.com]

are these columns in any specifc format, or are they the same data as the
other columns?

 

[the1859]

They are in the same format as the other columns that do appear.