I ran into an issues while trying to launch a PlayBook app from Flash Builder Burrito in Debugging Mode.

I launched and the "Launching [Application name]" indicator in the bottom right corner just slowly inched up to 100%, but nothing happened. Eventually I got error messages.

From Flash Builder:

The Flash Builder debugger failed to connect to the running application.

Ensure that:

1. For in-browser applications, you are running the debugger version of Flash Player.

2. For debugging on a mobile device, you have a reliable WiFi connection to the device, and port 7935 is open on your machine's firewall.

On the emulator:

Unable to connect to the debugger at address x.x.x.x, enter the correct host name or IP address or select cancel to continue without debugging.

The cause of this error is that your Default Debug Host IP is wrong. To get to this setting:

Go to Flash Builder Preferences
FlashBuilder ->
Target Platforms ->
BlackBerry Table OS

In my case the reason the error happened was a bit confusing. But it came down to this. That IP address got set to my public IP address in my hotel. When I went to present I didn't have a network connection, and so that address was no longer present. The easiest fix for this when using the emulator is to set that Default Debug Host IP to the gateway of your VMWare's NAT setup.

I don't have an easy was of getting that, but the way I did it was:
Determine IP address for Playbook emulator
BlackBerry Settings
About ->
inet

For me 192.168.253.138.

Determine all of my system's IP addresses
OSX ifconfig
Windows ipconfig

When I did that, I found one address (192.168.253.1) that was a reasonable bet for the gateway of the NAT network.