Comment #1 on issue 151 by ingenthr: Append/Prepend to existing key whose value that grows larger than 1MB and non-existing key returns NOT_STORED error
http://code.google.com/p/memcached/issues/detail?id=151
The problem with this is that other clients may be expecting different behavior. There have been problems in the past with changing responses. I don't know enough to anticipate how it would affect most of the clients.
I think this makes sense to do in 1.6 with an envvar to get the old behavior if needed.
In terms of addressing your current needs with 1.4.5, perhaps the client could fail back to doing the append on the client to see if it's a memory issue or another kind of issue.
