Truncate failing with 1.0 client against 0.7 cluster

[Guy Incognito]

i'm doing an upgrade of Cassandra 0.7 to 1.0 at the moment, and as part 
of the preparation i'm upgrading to 1.0 client libraries (we use Hector 
1.0-5) prior to upgrading the cluster itself.  I'm seeing some of our 
integration tests against the dev 0.7 cluster fail as they get 
UnavailableExceptions when trying to truncate the test column families.  
This is new behaviour with the 1.0 client libraries, it doesn't happen 
with the 0.7 libraries.

It seems to fail immediately, it doesn't eg wait for eg the 10 second 
RPC timeout, it fails straight away.  Anyone have any ideas as to what 
may be happening?  Interestingly I seem to be able to get around it if i 
only tell Hector about one of the nodes (we have 4). If I give it all 
four then it throws the UnavailableException.