was you using tiscali before & how long back was it you was using winmx ?
tiscali are well known for packet blocking and throttling of winmx a friend of mine changed to them & no matter what they cant connect to winmx now even though a while back they could (basicly they are a pain in the ass)
also have you re-allowed winmx in your security as a new install often requires this (try starting winmx with it turned off to check if this is so also make sure you are not running the xp firewall as well as this will cause probs)
did you also do a complete fresh install e.g delete the c/drive >> programme files >>winmx folder ?