Problem with interlock and memcache-client

hey all

I have interlock and memcache working fine in one rails app. I'm
starting another and can't get it working - when i try to run a test for
example i get

no such file to load -- memcache-client
...list of rubygems require error trace messages
<app folder>/vendor/plugins/interlock/lib/interlock/config.rb:96:in
`install_memcached': 'memcache-client' client requested but not
installed. Try 'sudo gem install memcache-client'.

I don't understand what's going wrong here as i have the memcache-client
gem installed. I've even successfully unpacked it into the vendor/gems
folder of the app to no avail. On closer inspection of interlock, the
actual error that triggers the rescue message above is "Anonymous
modules have no name to be referenced by" which is triggered by this

if MemCache.constants.include?('SVNURL')

So, MemCache is an anonymous module here? I don't even know what that
means, apart from that it's what you have inside a block.

Basically though, before the crashing line, i can't even inspect
MemCache without causing an error.

Grateful for any advice...thanks, max