Ann, welcome to BBBB! The fact that it happens at the exact same time on both computers, using different screen names certainly seems to point to an event related to your system. I just want to be clear that it's not Yahoo that stops working completely, but your text isn't visible once you hit send, and you are not receiving text back from your contacts. If the program itself is shutting down that could be something very different.
May I ask what router you use, what operating system you are on, what firewall you have installed on both machines, and which anti-virus and anti-spyware programs you are running? I'm thinking there may be some kind of a conflict somewhere. Also, do you have any other browsers installed?
I might suggest running a
HiJack This Log and you can PM it to me. Please copy and paste it in, do not send it as an attachment. I've generally found this problem is browser related and perhaps I will find something on the log that may point us in the right direction.
Be patient, I'm pretty sure we can get this cleared up. It may take a few days and we may try things that don't work, but I'll give it my best shot. Can I also assume you have run a complete virus and spyware scan with current up to date definitions, and you have disabled any and all pop-up blockers in IE and all your toolbars?
I'll look forward to hearing back from you.
-Doris-