Trying your hello example creates "b has no properties" error in MicrosoftAjax.js line 5.
When changing script source from MicrosoftAjax.js to MicrosoftAjax.debug.js is says:
Chyba: [Exception... "...
Id #4997 | Release:
None
| Updated: Jan 6 2008 at 12:47 PM by Dzonny | Created: Jan 6 2008 at 10:48 AM by Dzonny