One of the customers has found the JS error:

"We think we discovered a bug in icefaces framework. On some pages and some slower computers only the browser doesn't update to show the requested page. In these cases there is an exception thrown in javascript. It seems this is a race condition happening only on slow computers or with slow connections. See this client side trace for details:

PROTOKOLL: [window] persisted focus for element "mainForm:dataTable:2:commandEdit"
PROTOKOLL: [window] applied updates >>
update["menuForm_fixviewstate"]: <span id="menuForm_fixviewstate"><script....
update["mainForm_fixviewstate"]: <span id="mainForm_fixviewstate"><script....
update["popupForm_fixviewstate"]: <span id="popupForm_fixviewstate"><scrip....
update["v35ftku12-retrieve-update_fixviewstate"]: <span id="v35ftku12-retrieve-update_fixv....
update["v35ftku12-single-submit_fixviewstate"]: <span id="v35ftku12-single-submit_fixvie....
update["dynamic-code-compat"]: <span id="dynamic-code-compat"></span>....
update["javax.faces.ViewState"]: -1942842512171281115:-144552365287784559....
extension
PROTOKOLL: [window] full submit to http://localhost:8080/CarrierPortal/pages/acd/group/AcdGroups.xhtml
javax.faces.execute: @all
javax.faces.render: @all
javax.faces.source: mainForm:dataTable:2:commandEdit
view ID: v35ftku12
event type: click
SCRIPT5022: DOM Exception: NOT_FOUND_ERR (8)
AcdGroups.xhtml, Zeile 1 Zeichen 1
PROTOKOLL: [icepush] received noop
PROTOKOLL: [icepush.838ad.async-connection] closing previous connection...
PROTOKOLL: [icepush.838ad.async-connection] connect...
PROTOKOLL: [icepush] received noop "