Warning: Invalid argument supplied for foreach() in MemCacheDrupal->wildcards

This should only ever be an array, did this problem last a long time? I would imagine restarting the memcache daemon would have fixed it. Leaving this ticket open to see if this is affecting other people, perhaps we need to be more defensive in this section of the code to handle evictions.

We are seeing this error in our logs even after restarting the daemon with the latest 7.x-1.x-dev so it would seem an array is not being passed.

Invalid cache id received in memcache.inc wildcards() of type integer.

Also seeing this error in the logs, which would also seem to suggest the array is being messed with. Also posting as maybe the two are related?

Notice: Array to string conversion in dmemcache_key() (line 984 of sites/all/modules/contrib/memcache/dmemcache.inc).

The error you're seeing in #3 was introduced in #1305696: substr() expects parameter 3 to be long, string given memcache.inc. A cid of type integer is likely valid so that could be a regression that needs to be fixed -- will be reviewed in the other ticket.

The issue in #4 was also fixed already. (The line in reference was rewritten, it was $full_key = urlencode($prefix . $bin . '-' . $key); when you saw this error.)