Vista - messages not being recieved

I am seeming to have a hit and miss situation with messages being recieved by
others that are are in my contact list. I have also had problems in the past
of seeing a contact online for a while and then not seeing them online even
though they are and that I haven't been blocked. and for some reason when I
have a contact delete me like if they are online,I can't see it until I sign
in again. this has been a recent thing that has been going on since the
glitch I had with the messenger giving me a prompt on a yahoo address when I
added it that it had already been added and adds it twice to the messenger
screen. are there any solutions or work arounds for this?