It is a reported issue of Aptana 3.2.2 (actual version March 2013)
Solution: revert to 3.2.x version or wait until 3.4.x is available (where is already fixed)
Detailed Info
After several checkings and research , I find out that there is a reported issue with the actual version 3.3.2
Issue labeled as:
Aptana Studio APSTUD-7636 Cannot show preview (embedded WebKit browser)
This can be seen here at appcelerator issue tracker where states the following
Expected Result:
Preview should be opened exactly as in previous versions of Aptana. Preview worked without errors in Aptana 3.2.X before updating to 3.3.1.
This was corrected for version 3.3.4 which at present (march 2013) I am not able to obtain. So I reverted to 3.2.2 which I downloaded from appacelerator wiki
Full package name: Aptana_Studio_3_Setup_Linux_x86_64_3.2.2.zip
I installed and the preview is working as it should
So: Until version 3.4.x is not available ill keep this old one 3.2.2 I hope that my research will be useful to someone else.