After upgrading to 6.9/6.10 some or all of your app pools will not start causing the web client to not function properly. You may come across the error "DocuWare App Pool Identitiy is Invalid" even though the app pool is set to a local or domain admin.
The cause is that the AppPool User which usually is a member of the Local Admin Group, has no rights to "Logon as Batch Job"
Go to secpol.msc > Local Policies > User Right Assignment > Logon as Batch Job
Add Group "Local Administrators"