If there are no errors in the browser and everything is operating as expected, I'm not sure what would be producing the errors except a spider of some sort.
I believe the only line that could produce the "id.bigimage.cat..." error would be in showphoto.php and the line doesn't match what is in my 4.8d as it would have quotes around the userid (are you sure your files are up to date?)
I believe the other error is also sent my showphoto.php; but I believe this may be a spider calling addfav.php without a variable as it is trying to spider the page.
Please do not PM me for support or sales questions. Thank you for your understanding.