Our environment consists of 6 memcached servers running on Solaris 10 boxes and application code running on a mix of Solaris and Ubuntu servers. We are running into issues accessing data set on one operating system and accessed from the other. The only instance where the keys can be accessed from either OS is when we only connect to a single cache server and not the pool. As soon as you add 2 or more servers into the pool all keys are only available on the OS they were created on.
Cache pool is all memcached 1.2.6 and application servers are running memcache PHP library at 1.86. All the servers in our Solaris and Ubuntu environment are 64bit.