I was reading some of the theories, and something dawned on me, what if, someone used the dice ter'angreal on Mat? But wait, there's more. After that first time in Tar Valon, Mat's luck seems to slack off a little. Maybe the ter'angreal started to wear off a little. Thus, Mat's luck isn't as phenomenal as that night. As for the rest, I think that the ter'angreal is weakening it's influence on Mat, as it has been - how long? - since Mat was Healed, and it must be weakening a little. However,I think that his ta'veren-ness has 'adopted' the effects of the ter'angreal, and the luck itself, although not as strong as that last night in Tar Valon (sounds like a great song title, yeah?) his luck still runs in streaks, signified by the dice rolling in his head.