Advanced poll - number of questions and cookies

Hi,

First, sorry for my poor english

I've installed Advanced poll and i've a little problem.

My index.php contain 29 poll questions and i want to use the cookies.
When a user vote 20 of them ... no problem. the cookie contain all info and he see he have already vote.

If he click on the bouton of the 21th question. the informations of the first poll seem to be erase in the cookie.
If he vote the all 29 , ... 9 of them contain the vote button and he can re-vote.
Only the 20 last vote informations are in the cookie.

AP is limited in the number of question ? ...
...Or ... is there a parameter i haven' see ?

Thanks

Sharo