Flashing isn't that bad. That usually means that the Slingbox is at least trying to get an IP address but it can't.
I've noticed that Slingbox has a problem getting an IP address from some routers. Especially the ones that have had the manufacturer firmware replaced with the third-party linux kernal, like DD-WRT or Tomato. In almost all cases, either a firmware update or returning the to the original manufacturer's firmware resolved the issue.
Another suggestion bring the Slingbox to a friend's or neighbor's home. See if their router will assign a DHCP address to your Slingbox. If so, then configure the Slingbox with a static IP address that is suitable for your router. That way you can return and plug back in and not have to worry about DHCP incompatibiliteis.
Finally, as I understand it is not entirely uncommon for malfunctioning AC adapter to cause the symptoms that you've described. On the bottom of the Slingbox, you should see the power requirements; voltage, amps, and polarity. If you have a compatible power supply then you can test it with your Slingbox to see if there's any change.