I tried to do a install of 5.5 and 5.4 on this same system.  The anaconda
 
graphical install wizard did not come up and the screen went blank.
I installed using the text interface and the install finished but,
Like in your case, starting X hangs the system.
I worked around this issues by installing 5.0 the updating to 5.5

Just thought I would post to the community that there is still an issue 

with 5.5 and that I also got a hang when using the graphical installation
 
interface.

Cheers