As of right now, Java 7 is not compatible with Oracle EBS.  All Oracle users must make sure that they do not upgrade to Java 7, at least for the time being.  This can be done by...

If I already upgraded to Java 7, what do I do?

If a user has already upgraded to Java 7, then he/she has to be downgraded to Java 6.  

Link to Java 6 download (Windows):  http://java.com/en/download/manual_v6.jsp

Link to Java 6 download (Mac):  http://support.apple.com/kb/DL1550

Why is this required?

If a user has Auto-Update enabled, the JRE 1.6 version will be updated to JRE 7.  JRE 7 has not been certified with Oracle E-Business Suite yet, which means that functionality based forms (e.g. Financials and HRMS) will stop working if you upgrade to JRE 7.