Lefteris,
Using the exact XML you provided I had no Issue. Do you have the layer visible in the map?
[ATTACH=CONFIG]23055[/ATTACH]
Mike,
I just started a brand new compiled site on my IIS and copied over the 3.3.2 compiled Identify Widget over to it and and it worked fine....
Guys,
I will be releasing a 3.4 version (hopefully in a week or two) of the widget that has full application builder integration (this means I can eliminate user xml configuration errors). All I can say is you have an issue in your configuration of the widget as I don't have any issue getting it to work.