i think you allready know alot of reasons because you ve had this problem before right??
first things that come to mind is .. your internal ip was not set to be static inn hte past and it has changed, wich means the ports in your router are opened to the wrong ip now
.. your windows firewall was switched off and some reason was switched back on without you knowing
.. you have installed something protective wich is now blocking winmx
i would go for the first in the list
, please read back for the how to's in your older thread about this
if all this is not the cause please try and give as much info as you can, like how you re connected, whats your operating system, what protection software do you use, anything new installed lately? , do you get a roomlist etc etc