Can you check whether you are using recommended internet explorer to access the EBS. Review the support IE browsers.
Recommended Browsers for Oracle E-Business Suite Release 12 (Doc ID 389422.1)
This happens to me in I.E. usually after a refresh but sometimes happens in Production as well. The solution is to fully close all iI.E. windows, kill any iexplore.exe left over processes from task manager and restart. If that doesn't work, you will have to stop I.E. again, clear all Temp files Internet Options then restart. Usually just a full restart works.
I restart the application
restart my pc
restart the server OS