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
