so the blank gray page is that tomcat started, but vCD's core engine did not come online.
stop all cell services (service vmware-vcd stop)
1. delete any *log* in the logs folder
2. start the cells
3. tail -f cell.log (see if it just stops at some point, or repeats messages)
4. provide the cell.log and vcloud-container-debug.log on the forums
you probably missed some core requirement when setting up the cell. e.g. forward and reverse DNS lookup. The cell will do a name lookup based on the IP to see how to log some information. this is just one example out of many that could be in the startup of the application.