Simply put, I have copied a column of numbers from one program into an excel
spreadsheet. Most of the time this works just fine, but this time, in order
to preserve text formatting in one of the columns, I set the destination
cells to a text format, then pasted the numbers. They will not add and
formulas referencing the cells evaluating to a non-formula string.

If I set Text Format after the paste, this problem does not occur. No
amount of format reset seems to restore the preformatted cells to a useful
state. Manually keying in new numbers works, but cut and paste seems like,
on the surface, such a useful tool.

My question is not how to work around this. I have already done that. As a
matter of curiousity, I would like to know what is going on here that these
values become unusable.

Thank you,