MembaseClient does not Set values consistently

I am using MembaseClient from Enyim Memcached client libary to store objects in Membase Memcached Server. Below does not work consistently, assertion fails most of the time. Am I doing anything wrong?

// File size is 360kb
var reader = File.ReadAllText(@"c:\RHDSetup.log");
for (int i = 0; i < 10; i++)
{
Assert.True(new MembaseClient(c).Store(StoreMode.Set, i.ToString(),
reader));

Thread.Sleep(1000);
}