I've been running 0.10.0rc1 for a couple weeks with no problems until now. It's stuck on block 339768, hash 0000000000000000160483c084b185b87e974467e0f684a1b26cc555174b59c7, currently about 7 hours old. I have 34 peer connections and ~33k transactions in my mempool. In debug.log I'm seeing a lot of AcceptToMemoryPool errors; not sure what else to look for.
This is on Linux x86_64, using the binary downloaded from bitcoin.org. I've confirmed I'm not out of disk space.
I notice there's an rc3 up now, but I'll hold off on restarting or upgrading in case there's anything you want me to try first.