Corrupt listener in IS SAP Adapter

On a number of occasions a SAP listener has gone to an orange state, attempting to stop it generates a java error message (sorry do not have text of this). The start then fails. The only resolution we have found is to delete the listener and recreate it.
Has anybody else encountered this ? If so what was the cause/solution ?

In the 4.0 version of the SAP Package this could happen in cases when the RFC Listener connected to the R/3 system via a firewall (SAPRouter). The problem was caused by the firewall cutting the TCP/IP connection without the RFC library noticing.
Should be fixed with the new RFC library which comes with the 4.6 version or one of the later Service Releases for the 4.0 version.
Regards, Ulrich