Just to conclude this thread or my contribution to it, my problem appeared to be related somehow to using SU through a Linux machine that is remotely controlling a Windows PC where the instance of SU is installed and running. Not sure I said that right, but you probably understand. The system we use to provide Windows on a Linux desktop is Citrix, which I understand is not really a Windows emulator but actually a remote control of the distant Windows pc. However I also understand the same sort of problems with exporting animations happens with the Windows emulator Wine (I think it's an emulator), as reported in the link a few posts above.
If this thread would fit better somewhere other than Newbie, then feel free to refile it.