What Prompted Yushchenko?

Ukrainian President Viktor Yushchenko has accused Moscow of hindering the investigation into his poisoning in 2004. What’s more, he hinted that Russia might actually have been behind the poisoning. An indignant Viktor Chernomyrdin, Russian ambassador to Ukraine, said that Russia was not involved and suggested that Ukraine should solve the crime on its own. Somewhat later, however, Ukrainian officials said that Russian investigators had signaled a readiness to cooperate.

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Chernomyrdin’s [russia's ambassador to ukraine] reaction was very emotional. “Why suddenly such serious accusations?” he wondered. “Why should we investigate it? Settle it on your own. Someone always hinders you,” he told a group of Ukrainian journalists in Kyiv. A high-placed source at the Ukrainian Foreign Ministry told Kommersant Ukraina that Chernomyrdin “should be punished for his arrogance” by the Kremlin or even replaced. Yushchenko’s secretariat accused Chernomyrdin of incompetence. “The Ukrainian president believes that Mr. Chernomyrdin’s statement was his own opinion, not reflecting the official position of the Russian Federation,” the deputy head of the secretariat, Oleksandr Chaly, said on September 12.

So what's going on here? Is Yuschenko just frustrated? Or is he doing an indirect dig at Yanukovich's Party's 'relations' with Russia? Or something else happened? It is intriguing though!