The backup was made prior to upgrading to 6.3.2, and you don't have a more recent backup?
You didn't say which version you upgraded from, so depending on that, the w3t_PollData table may have changed enough that the one in the backup would not be compatible with 6.3.2. Dealing with that may be possible but could be messy.
To create an empty w3t_PollData table, just run (from the phpMyAdmin SQL function) the query from createtable.php that creates the table:
CREATE TABLE w3t_PollData (<br /> P_Name varchar(75) NOT NULL default '',<br /> P_Number int(4) unsigned default NULL,<br /> P_IP varchar(75) default NULL,<br /> KEY pollndx2 (P_Name)<br />)
1) If your table prefix is something other than "w3t_", change it in the query above.
2) As a precaution, do a complete database backup before running the query.
3) Close your board while doing the above.
Of course, there are probably posts that reference polls that no longer exist, so you'll get database errors from those.