Hi @edu_ ,
Has this been resolved? I ran into the same issue using three of the last VM installations:
From a fresh Virtualbox import I log into the default user "user" and create two tasks. When I try to merge the two tasks the "Merge Duplicates Into This Task" window does not show the other task, even with "All open object" in the drop down box.
This is also an issue on your "Demo in browser" instance. The Phabricator demo at https://www.phacility.com/ does not have this behaviour and work correctly.
EDIT - 20160726-12:07
This issue does not seem to present when using Internet Explorer.
Using Chrome you get the following error:
Uncaught Error: JX.initBehavior(map): behavior(s) not registered: phabricator-object-selector core.pkg.js:193