This is something that I noticed because of what I do. You can sign into GTalk in multiple locations, so when someone sends you a message it would show up on all the computers your signed into. So in my case the message pops up at home, then the Desktop PC in one office at work, and my laptop at the other office at work. And sometimes if your computer is acting up you might here a ding, but it wont show up except at the other places so it will be satisfied that the message went through but you didnt know. I see it sometimes happening to me, and if there is a hang-up on your end it acts normally on the other computers so even if you disconnect and the other PCs are still signed in then the person your talking to will assume your still signed in but nothing is showing up. Well I thought I would mentioned it since with other chatting programs once you sign in at one place it disconnects the other, but honestly I prefer the way GTalk is, but I find it funny when it does this!