Thanks Stijn for sharing the info; this issue appears to be consistent across app servers: Richfaces 3.1.6 has this same problem with JSF 1.1_01 - Reference Implementation on Weblogic 9.2.3. I followed this post, downgraded to Richfaces 3.1.5 & JSF postback started to work fine.
However, Richfaces 3.1.6 works well (on this issue of handling page postbacks) with JSF 1.1_02 Reference Implementation.
Hope Richfaces release notes specifies the minor version of JSF implementation that they support, in future.
Ah. Good to know it's not just the OC4J server having trouble with this.
The application has been developed now, but for future ones I'll keep in mind to give RF 3.1.6 a shot with the JSF 1.1_02.
Thanks for the info! :-)