OK. Forget what I asked/stated in my previous reply. It doesn't work. I had a similar problem today, except I am using two processes where the second process is relying on the first process to create a text file. The second process was firing off while the text file was being created; therefore, raising a similar error you're getting. I resolved my issue by having the first process export the text file as CREATING_TextFile.txt, then using the distribution feature to move the file and rename it to the file name that the second process is monitoring.
This might not help you in your situation because you're only using one process, but maybe there's a way you can write a script or batch file that monitors the completion of the file and renames the file. Then you can set your process to monitor the newly renamed file. Then again, that might not be an option for you. Just a thought. Sorry I couldn't help, but maybe it'll give you some ideas. This is an issue I've brought to Datawatch several times before with the idea of including a way in the file monitoring setup to delay the process once a file was detected. But I think it fell on deaf ears.