The usual cause of this is the fact that cursor behaviour in TimesTen is different to that in oracle. In TimesTen executing a commit or a rollback will close all open cursors on the connection where that operations is executed. A subsequent attempt to use (e.g. fetch from) such a cursor will typically result in this type of error.
Could it be that under some circumstances the PL/SQL logic, or the application logic that calls it, may have executed a commit or rollback which has closed cursors and then the code has subsequently tried to use one of those cursors without re-opening it?