I'm going to chime in here and put in my vote. I think Nick C is absolutely correct and have always interpreted the Rule this way for as long as I can remember.
My reading of RROP is the same as Nick's and I have always thought it was clear on its face. I can appreciate that people have tried to compare and contrast language (e.g. what "opens" the betting, what is an "action", etc.) from different rules of the set to try to make a contrary case, but let's face it, RROP wasn't written or vetted by a lawyer. Perhaps we need a lawyer to correct the "inconsistencies", if they do exist. ;-) In any event, I doubt that the author originally put much thought about whether "act", "action" or all other similar terms should share similar properties across all rules.
For example, I don't think that "reserving the right to act" necessarily means "reserving the right to raise" or "reserving the right to act with all actions available to the players as if he had not checked", for example. I would contend that the "reserving the right to act" language, for that particular rule, was simply meant to mean that by checking, you are not folding. It is a description to the layperson of what is meant by "check". The player will still have options to do something when it comes around to that player's turn again... but there's nothing to say about what options those are, and certainly it does not explicitly say "all betting and raising options". For that you have to rely on other rules.
I feel it really is a stretch to try to interpret the rule in such a way that player A can still raise a short-all in after checking, but in any event, I think it is at least within the spirit of the rule that such an "angle" (being allowed to check-raise a short all-in after checking) should not be permitted. So perhaps we should focus on what the rule should be if it isn't actually 100% clear to everyone what it is supposed to say.
I believe that by "checking" rather than "betting" when both options are available to you, you are forfeiting your right to raise a less-than-a-full bet, in the same way that by "calling" instead of "raising" when both options are available to you, you are forfeiting your right to raise a less-than-a-full raise. I don't see why the checker should have more options than the caller, when the relative differences between the opponent's wager and the checker/caller are of a comparable order of magnitude relative to the minimum bet size for that round.
In my view, when you check, you are essentially saying "I Bet Zero". You can decide to call me by "Calling Zero" (check), or you can "Raise" my bet of Zero. If you raise my bet of Zero, then you are obliged to make the minimum raise (which is betting at least the BB). If, however, you cannot make the minimum raise over Zero because you are short, you can go all-in for less, and the "Bet Zero" player will not be able to raise if no one else has raised by the time action gets back to him (applying the "normal" rule). If you think of a check as "Bet Zero" (which I believe has historical basis although of course it's difficult to prove that now), then it is clear that the initial checker should not be able to raise a short all-in, by applying the other rules as you know them. Maybe this is "old school" thinking, but I think it is right.