The system is looking for the letter "x" between the cultivar names.
In the case of that first one you linked to, the "x" was actually not an "x" (even though it looked like one). It was actually a sideways cross that I guess was created Word or something? I'm guessing that instead of typing in those parent names, you may have copied and pasted it from somewhere. Whatever you copied it out of, they had it as a sideways cross instead of an X.
This is an odd issue that would only occur in that specific kind of situation. I fixed it by editing that particular plant and changing the character to a real "X".
