undefined method `incr' for <MemCache: 1 servers, 1 buckets

[andrew at flypublishing.com]

undefined method `incr' for <MemCache: 1 servers, 1 buckets, ns:
"myName", ro: false>:MemCache

Hello, I'm using the Ruby API (memcache not Ruby-MemCache) and I keep
getting these undefined method errors for certain functions.  The
"set" function works fine, as does the [key] get function, but 'incr'
and 'add' both give the error above.  Any ideas?  Thanks.