Dolphin 4.14.1 under Xubuntu 14.10 often hangs when copying and moving large files to and from smb-shares and attached storage. Command line operations and other file browsers work fine under these conditions. Does anybody have a suggestion?

I think it's the preview - it seems only a problem when the remote path is opened. Maybe due to file watching.
You can btw. simply close the dolphin window, the copy happens in a kioslave process.

It is not that the interface stops, Dolphin crashes and the file operation is stopped. It forces me to use Thunar, rsync, etc. No problem, it is just that I like Dolphin for its human machine interface.

crash -> backtrace ("developer information") and file a bug
If size related, it sounds like some cache would run OOM.