trouble voting on polls

Everytime I try to vote on a poll this screen comes on:

vBulletin Message
The action you have attempted could not be performed as your session appears to be invalid. Click the below link to attempt this action again with a new session.
Try this action again!

Does this mean that the poll is compleeted? A similar and sometimes the same screen will apear on a new poll?

Never seen that message, I have no idea why it would do that. I hope that you have better luck soon.

I have that same problem!! I don't understand it!! I just tell people to vote for me.:)

I just post my reply since I can never vote.