I've had zero problems with IE8 or win7. While I haven't spent a ton of time on the OS, I have used it to connect to work and spent a couple of days using it intensely. No disconnect issues or problem.s
For the record, if you're on Windows 7, you're on IE8 by default. I'm running Windows 7 RC1 on my work laptop without any issues whatsoever. Can you be a little more specific than "disconnecting itself"?