Although this did not fix the problem, your message triggered more thoughts.
The data is in a table (.xlsx file in 2007). When I went to the design tab,
I changed the dimension of the table to include some additional columns.
Now, I can turn filter back on and sort by those columns. This answers the
problem for the short term.

I guess I need to just figure out how to turn the table OFF though and my
default stuff will start working again.