Forum polls, all permissions set properly but some users in same group can not vote
 

It is bizarre. I post a poll, as admin i vote fine, some of my subscribers vote fine, some of my subscribers can't vote.. I have compared the ones who can and can't vote and their permissions are identical. they click vote and the page refreshes and nothing happens. Is this a known issue? I can't seem to find any info about it. I tried setting poll permissions to "No" then back to "Yes" but did nothing. Thanks for any help