Platonism lead to Skepticism?

Have a look at Belief and Truth by Katja Vogt, who is Professor of Philosophy at Columbia University.

In Belief and Truth: A Skeptic Reading of Plato, I explore a Socratic intuition about the difference between belief and knowledge. Beliefs, doxai, are deficient cognitive attitudes. In believing something, one accepts some content as true without knowing that it is true; one holds something to be true that could turn out to be false. Since our actions reflect what we hold to be true, holding beliefs is potentially harmful for oneself and others. Accordingly, beliefs are ethically worrisome and even, in the words of Plato’s Socrates, “shameful.” As I argue, this is a serious philosophical proposal. It speaks to intuitions we are likely to share, but it involves a notion of belief that is rather different from contemporary notions. ...

I argue that the ancient skeptics and Stoics draw many of these ideas from Plato’s dialogues, revising Socratic-Platonic arguments as they see fit. Belief and Truth retraces their steps through interpretations of the Apology, Ion, Republic, Theaetetus, and Philebus, reconstructs Pyrrhonian investigation and thought, and illuminates the connections between ancient skepticism and relativism, as well as the Stoic view that beliefs do not even merit the evaluations “true” and “false.”

Personally, I think the thing that is missing from most discussions about scepticism, is that scepticism arises from the intuition that the world of common experience is in some sense delusory. That is a completely different attitude to today's scientific scepticism.

Quoting anonymous66

Can anyone sum up for me just how it is that Plato's School (the Academy) eventually became the school of skepticism? It seems to me that If Forms, then Not Skepticism. And Plato argued for the forms. Were there adherents of Platonism who argued with the Skeptics?

Lets take a look at Diogenes Laertius' "Lives and Opinions of Eminent Philosophers:

[i]I. ARCESILAUS was the son of Seuthes or Scythes, as Apollodorus states in the third book of his Chronicles, and a native of Pitane in Aeolia.

II. He was the original founder of the Middle Academy, and the first man who professed to suspend the declaration of his judgment, because of the contrarieties of the reasons alleged on either side. He was likewise the first who attempted to argue on both sides of a question, and who also made the method of discussion, which had been handed down by Plato, by means of question and answer, more contentious than before.[/i]
-Book 4.

VIII. He seems to have been a great admirer of Plato, and he possessed all his writings. He also, according to some authorities, had a very high opinion of Pyrrho.
-Ibid.

So there you have it. One of the scholarchs also was a fan of Pyrrho. Simple as that.

Sextus Empiricus notes:

Arcesilaus, however, who was, as we said, the president and founder of the Middle Academy, certainly seems to me to have shared the doctrines of Pyrrho, so that his way of thought is almost identical with ours. For we do not find him making any assertion about the reality or unreality of anything, nor does he prefer any one thing to another in point of probability or improbability, but suspends judgment about all. He also says that the End is suspension -- which is accompanied, as we have said, by "quietude." He declares, too, that suspension regarding particular objects is good, but assent regarding particulars bad. Only one might say that whereas we make these statements not positively but in accordance with what appears to us, he makes them as statements of real facts, so that he asserts that suspension in itself really is good and assent bad. And if one ought to credit also what is said about him, he appeared at the first glance, they say, to be a Pyrrhonean, but in reality he was a dogmatist; and because he used to test his companions by means of dubitation to see if they were fitted by nature for the reception of the Platonic dogmas, he was thought to be a dubitive philosopher, but he actually passed on to such of his companions as were naturally gifted the dogmas of Plato. And this was why Ariston described him as "Plato the head of him, Pyrrho the tail, in the midst Diodorus"; because he employed the dialectic of Diodorus, although he was actually a Platonist.
-"Outlines of Pyrrhonism" book 1, ch. 33.