If you're saying that with the form open and valid values entered, you run the query and it is fine, but if you THEN click to open the report (i.e. you don't close the form or do anything else) and it isn't fine, then perhaps the issue is in the button code. Maybe post that code - please use code tags (# on posting toolbar) with indentation in the code.
Code also be something about the report and it's code if there is any (e.g. a filter being applied sometimes).
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.