omg help us windows live messenger issues

ok heres the problem our internet connection is working fine, but if we
double click on the windows live messenger icon or try to get messenger to
start up at all it wont. we have three pcs hooked up to the same modem via
router and all pcs are having the same issues. now mind you we can sometimes
get into messenger its just when our pcs feel like it. lol. other times it
can take hours to get it to pop up on the screen. if this sounds confusing
believe me it is. any way we had a new modem pup in because we were having
internet problems but now this...if you have any suggestions that may help
fix this issue i would greatly appreciate it