Please check the Forms, Application and DB log files for more information and post them here if you find any interesting information.
Can you provide the list of patches you have applied?
In addition to the log files mentioned above, please confirm that you have no invalid objects in the database.
Loading the System Administrator Forms Responibility Produces Error FRM-40735,ORA-06508 (Doc ID 271652.1)
Oracle Application Return The following Error FRM-40735: ON-ERROR trigger raised unhandled exception ORA-6508 (Doc ID 797293.1)
After Migrating To Linux, Users Are Seeing FRM-40735 When Trying To Access Forms. (Doc ID 1282488.1)