Shoutbox

At times I have the msn live plus..but then when i restart my computer it is no longer on, but is still on my desktop, so i click it to try and reinstall it back on my msn, but it gets as far as the actual installment..then 1/4 of the way through it stops. The message says that An error occured while trying to access the files of Messenger, and to exit and try again or restart. I restart and its just the same thing. But sometimes a few days after i restarted my computer it comes back... How can i fix this problem!!!

Thanks!