If you mean last post appearing with a date/hour not in concordance with the date/hour appearing on this same last post, that's because the date/hour given in the main page is actualized everytime anyone votes, regardless of he/she posts anything or not.
So, if you vote on a poll whose last post is from 2006 (to give you an example), on the main page it will appear as last post being on the day/hour of your vote, but if you look at it, you'll see the last post being done in 2006.
If you mean the many poll threads appearing on the "Lastest posts" listing, this is probably because someone(s) have been Reading them and voting on them, so activating what I said.
This aside, I see nothing weird on them. If that was not what you meant, please, specify what you were alluding to...