Assuming the rest of the form controls are bound to the same query as the misbehaving control, I'd reset the control source to any other field in that query, even if you already have it bound to some other control. If you then get data in the control, there could be an issue with the expression, which you should post. I'd switch it back and see what happens. If you don't get data from another field, I'd replace that control (delete, save/close/open, add new textbox). I looked for the obvious, such as having the same name for the query field and control, Name Autocorrect, but your textbox seems to be named Text100 or something like that. Form corruption is another possibility, since you should be able to bind a calculated query field to a textbox.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.