My windows messenger problem

Hello,

hello
3 days ago i download windows live messenger version 8.1 (if not wrong)
but,now i have a problem with the windows live messenger..
it can't login..


"windows live messenger has made several failed attempt to sign you in.
your firewall maybe blocking Windows Live messenger from connecting to the service.
please revies your firewall settings.see the retailer's construction for more information"


my firewall have a problem??
how can i actived my firewall??
what should i do first??

what problem with my windows??
help me plizz..


sorry if my english not very well..

thx b4..