I previously joined a domain using likewise-open 5.4 on Ubuntu 10.04. Then I left the domain using likewise-open, and switched to using samba to join the domain. Now when I lock the computer and try to unlock it when the network connection is slow or if the domain controller is down, it will hang forever - until the connection is fixed or DC comes back online.
I have another Ubuntu 10.04 server with an identical samba configuration to join the same domain - and it works perfectly. The only difference is that this other server never had likewise-open installed.