Sometimes these executables doesn't work with server memory problems also. Last week we had the same problem with svrmgr/sqlplus executables. It will come out after 3-5 min
you type in exit. Again its resolved on its own after 24 hours. Its strange. Noone did anything.

If you wanna test this, use your load from somewhere else using connect string.

Call sqlldr from sql script. Connect to sqlplus using another box executables and call that sql script.