I have faced the same error while opening Sql Developer bundled with the Oracle 11g in win 7 os 64 bit machine.
I fixed the problem in two steps :
1. Installed Windows x86 JDK (32 bit) from
2.Open G:\app\product\11.2.0\dbhome_1\sqldeveloper\bin\sqldeveloper.con file in notepad (I have installed Oracle db in G directory) and Change the path SetJavaHome C:\Program Files (x86)\Java\jdk1.7.0_25. Save the file .
Done..!! It worked fine..!