By any chance are you importing the data from another application?
Check out your numbers: does the cell contain an apostrophe and then
the number? This happens sometimes: if you are importing, and this is
the case, you may be able to adjust the output side of the other
application to avoid the apostrophe.

As a workaround for now, try this formula:
=--SUBSTITUTE(A1,"*","")

This should convert whatever is in your cell currently to a numeric
value. You can then copy the formula, and paste it as values over the
existing data.