dvdxcopy has two steps to do:
1. to read the original dvd, decss it, decode it and encode it, then save the streams and ifo files in temp folde on the hard disk (you can specify the location of this temp folder in dvdxcopy options). in this step it also creates a copyright warning screen and includes the screen in the ifo file.
2. it burns the streams/chapters to a blank dvd according to the ifo file.
so what you want to do is:
when dvdxcopy finishes step 1 and is waiting for the blank disk, you run ifoedit to change the ifo file so the warning screen is skipped. after you edit the ifo you let it continue onto step 2.
according what you said, your dvdxcopy is not working correctly. i don't know want you did. if dvdxcopy quits before you can edit the ifo, the problem is with dvdxcopy. you may want to do an uninstall/reinstall.
to make things simpler, use the platinum version in its "simple mode".
this method of warning removing worked on every dvd I copied.
btw, save the instruction page on my prior post. I will remove it tomorrow.