I have installed PPM version 9 with an oracle 11g R2 (126.96.36.199) DB. When I log into Primavera I get a blank screen. I see in the URL that the app is at the Navigation screen but all I get is a blank screen. I have tried using IE and Firefox but get the same result.
Some end users within my environment experienced the trouble you describe (seeing a white page after log-in) within PPM version 8 SP2.
Resolution for all of these users is to check the checkbox within settings of IE 6 and IE 7 to "Enable Native XMLHTTP Support."