These errors occurred usually due to forms connection problem or some internal problem, the solution is, close the form, re-connect to the database and then re-open the form.
FRM-10001: Internal Error: TOS.
Cause: Internal system error.
Action: If the problem persists, contact Oracle Support Services.
FRM-10002: Unable to save the current module.
Cause: Internal system error.
Action: If the problem persists, contact Oracle Support Services.
FRM-10003: Unable to retrieve the module from the file.
Cause: Internal system error.
Action: If the problem persists, contact Oracle Support Services.