You could run into a situation after the latest Java client runtime update, your R12 instance failing to load forms, complaining about the lower version of JRE. This is mainly due to the fact that, if your Windows OS is 64Bit, the latest java runtime update installs both 64Bit & 32Bit and most of the R12 environments run against 32Bit JRE.
Internet explorer (the only one browser that runs the JRE properly for EBS R12) loads the 64Bit java runtime by default from a 64Bit Windows OS & eventually the forms will fail to load.
At present the only possible solution to address this situation is to uninstall the 64bit version of java runtime, using “Programs and features” or “Add remove programs” based on the version of Windows you are using.
Hope this helps few out there :)