the conversation ended,....

[amul]

Dear friends


please help me with the following problem.

I have a list of items displayed in datatable.

i select two items from the table

when i navigate to edit page i have the buttons: save,next,previous,save&next and back

now i edit first item and click on save&next button.
now i edit second item and then click save&back button

i get "The conversation ended, timed out or was processing another request" message.

all the changes are successfully made but i get this message

[cosmo]

Post relevant source code(classes, views and pages.xml) of the isolated problem