Flash Build 4.0.1 - problem with debugger

After updating Flash Builder from 4.0 to 4.0.1 my debugger suddenly stopped working. There was errors both in debugging air apps and flash apps.

Changing Air version in descriptor to 1.5.3 does not make any difference. Also removing Flash Builder workspace was not a solution.

After two days I finally foud way to fix this problem.

1. Ensure that you have newest Flash Player with debugger installed in your browser (I am using Firefox)
2. Set new Flex SDK 4.0.1 to default
3. Create new Flash (not Air) project, in main MXML add one button with some trace(event) on click event
4. Run your application in debug mode, running slider in Flash Builder will probally stop at 57% and you will not see any trace on button click
5. Click right mouse button and select Debugger from popup menu
6. Select IP address radio and enter "127.0.0.1"
7. You should now see your trace message on mouse click
8. Also AIR apps should now work with debugging