Hmm... possible. I've never really checked. Maybe it's just coincidence that the ones I can't play are bigger than 320x240.
Edit : just did some digging, it seems naset is right. All youtube vids are encoded in FLV1 where the ones that I've got problems with are FLV 3 & 4. So then, I would surmize that ezxplayer limitation is : it will have problems with videos using FLV3 or higher. Which means I'll need a xcoder... hmm..
BTW. Anyone got FLV2 vids to test?