The Apology Difficulty is not the main concern in Scott Senn's piece, "Virtue as the Sole Intrinsic Good in Plato's Early Dialogues", but rather Senn's claim, evident in his title.
Now I haven't posted on that yet, because I haven't been clear about what exactly he means. Also, he sets his own view up against what he calls the Traditional Interpretation, which, insofar as I understood it, I could hardly believe was 'traditional'.
Anyway, this is what he says at the beginning:
When Socrates speaks of virtue, he is commonly--now almost universally--interpreted as having in mind a sort of practical wisdom, or some other power or disposition to act correctly. This assumption has led most commentators in recent decades to conclude that for Socrates virtue is simply a highly reliable, if not necessary and sufficient, instrumental means to happiness. The conclusion is expressed most succintly by Terry Penner: 'for Socrates the goodness of a human being is goodness at something, namely, getting happiness'. (I call this the Traditional Interpretation.) This in turn has led most commentators to conclude either that Socrates had no particular view about what constitutes happiness or that he simply fails to express (or to express adequately) such a view.
The Traditional Interpretation notoriously has difficulty making literal sense of some of Socrates' most important and famous claims, particularly in the Apology and the Crito, where he suggests that the person with virtue is self-sufficiently happy and invulnerable to all injury. The Traditionalist's difficulty is not adequately overcome even by taking Vlastos' further step [viz. of saying that, for Socrates, virtue is the major constituent of happiness]. After considering the problematic texts and some of the best attempts to solve the problem, I shall argue that the virtue Socrates speaks of in these passages must not be identified with practical wisdom or a facility for acting correctly and is not valued by Socrates simply or primarily as a means to--or even as the major part of--happiness. The virtue Socrates makes so much of is the sole intrinsic good, the sole constituent of happiness.