Reviewing the Service dialog it contains 17 tabs and 386 fields. This and possibly other records are being stored in the session which is cause it to exceed the memcache max size of 1 mb. Some research into the session object shows that the majority of data is being held in the workflow object. More research is needed.
*** Bug 1387715 has been marked as a duplicate of this bug. ***
*** Bug 1475574 has been marked as a duplicate of this bug. ***