yahoo messenger error

i really have a problem using yahoo messenger coz everytime i visit my email thru YM mail it caused error..and if i run the YM for a long time it caused many error like my outlook express won’t come out or any mail i’ll use, so i have to restart it again..is there any reason why? or any option for this? the other messenger i had was MSN but conflicts w/ norton virus..is there any possibility this conflicts too but there was no prompt like in MSN..