The only way I can imagine this being a browser issue is if it's something to do with the way a browser form is submitting data to the PHP file in question here, causing the form-processing code to follow a different logical path for some reason. Otherwise, once the script begins running, it should be transparent as to which browser its output is going to be sent to.
All I can suggest at this point is to search your source code for that message ("freeing resultout of fixit") and work backwards from there to figure out what condition(s) causes it to be displayed. Afraid that's the best I can do with the limited information (i.e.: I've never run into this problem before).