Um, from the picture that's *not* the cross-chain combo. He seems to be having trouble with small front/large rear, and that combo should be usable.
Easy to fix, just adjust the indexing for the front derailer. The indexing adjuster is usually a barrel knob near the shifter. To properly adjust it, you may need to back off on the lower limit screw if it's been set particularly zealously, but that may not be necessary.
Now if you get rub with the big/big or small/small combo, that is cross chaining and is a combo that shouldn't generally be used.