Yahoo Mail Beta - cursor moves up to the address bar when replying

I have used Yahoo Mail Beta with on several different computers with operating systems with no troubles up to the last several days, when on all the computers I use (meaning that the problem lies solely with the mail program and not the computer), the cursor moves up to the send to/address bar after I type the first few characters (usually S, L, K, etc). It must highlight the email address and before I notice it, I have typed over the address (sometimes losing it since it isn't in the text) and end up typing my text there. If I go back down to the message body, I can continue typing, but have to re-enter the email address. I've also found that if I copy the email address to the clipboard and then delete it from the address bar, I can type without any problems, then go back and paste it after I've typed a little bit. Anybody else had this?