On looking it up, there's confusion as to who was the source of this information: Was it his next-door neighbort? "Litvinenko's conversion to Islam was announced by his next-door neighbor, moderate Muslim and Chechen dissident Akhmed Zakayev..." Click here. Or was it his father? Click here and here.
There are also discrepancies as to whether he received the Muslim last rites or not - found within the above links.
If he had converted to Islam, that would strengthen my conspiracy theory that he himself was the source of the polonium - that he was a terrorist who was planting polonium in various places. Anyone who has ties to Chechen Muslims is automatically suspect, in my mind.
Chechens have been fighting for independence from russia [on and off] since the 1820s, way before anyone have heard of wahhabism. [The international angle is a very recent phenomenon there]. That makes them a bona fide liberation movement. Working with them could be logical for anti-putinoids, thus I do not see much suspicious stuff in it. The whole affair stinks of kegebuns.