Vista - Live Messenger sign in trouble

Hi I have been having this problem for a while.
Ill be running messenger on my laptop for a while and then Ill go away for a
bit, come back, and then when I try to access the messenger icon, nothing
happens. The loading symbol that comes up beside the cursor displays for a
split second, and the application does not start up. The problem goes away
when I restart the laptop. It seems whenever I come out of sleep mode the
problem occurs, however the problem occurs spontaneously as well. I received
help from Dell a while back but obviously it didnt work. Any suggeestions?
Thanks

Geoff