After having the problems with upgrading to firmware 2.1.80, I took the following actions last night. I pulled the power and restarted the slingbox with no fix. I then reset the Slingbox by holding down the reset button for about 7 seconds, until it re-started. After it finished its initial program load, I went to slingbox.com and set up the slingbox from scratch as if it just came out of the box. Frustrated, I waited until this morning to try it out again. On a wired computer in my house, I brought up the watch screen via slingbox.com. After a short time (5-7 minutes), It worked as before with streaming rates of about 8,000 kbps. I then powered on my laptop and connected via wireless to the slingbox. It worked. I was getting streaming rates of 5,000 to 8,000 kbps on a 54 Mbps connection.
After the upgrade the initial connection streaming rates were in the 100 kbps range. It started to go up but always came back down to that range after the upgrade. Once I re-setup the slingbox, the connection rates again started in the 100 kbps range but steadily came up to the 5,000 to 8,000 range after about 5 or so minutes. Now when I reconnect to the slingbox, my browser remembers the last streaming rate and starts off there, with good audio and video from the start.
I don't know if this will work for others, but mine is now running fine again.