nadine takahashi's page

I need clarification of the Spell Resistance rule, pages 564-565 of the Core Rules.

There is an argument about this rule. Some people say:

If I cast Magic Missile on a creature with spell resistance, if I roll under the creature's SR, I can NEVER, EVER, EVER cast Magic Missile on that creature. If I roll over the creature's SR, I can ALWAYS cast Magic Missile on that creature without having to roll for SR.

The problem is, the paragraph in the book is a tad unclear. The paragraph in question reads:

"Check spell resistance only once for any particular casting of a spell or use of a spell-like ability. If spell resistance fails the first time, it fails each time the creature encounters that same casting of the spell. Likewise, if the spell resistance succeeds the first time, it always succeeds. If the creature voluntarily lowered its spell resistance and is then subject to a spell, the creature still has a single chance to resist that spell later, when its spell resistance is back up."

There is more (a whole page) such as spell resistance being like an Armor Class against magic attacks but that paragraph above is the crux.

what I need to know is if the third paragraph is incorrect.