Axis2 Web Services Client in IBM Websphere throws "Error in key derivation" exception -

Axis2 Web Services Client in IBM Websphere throws "Error in key derivation" exception -

we have secure web service client(rampart) deployed in ibm websphere. facing scenario service provider (external) may go downwards frequently. our client works fine , can access service till goes down. 1 time provider comes after downtime, client throws exception :

org.apache.axis2.axisfault: general security error; nested exception is: org.apache.ws.security.conversation.conversationexception: error in key derivation

to recover need server restart, unacceptable. has had similar issue? pointer great help. in advance, ros

client websphere axis2 rampart