32 bit shuts down, 64 bit doesn't!

[Deanobats]

I have an old Dell Latitude D830 that I use as a test machine for trying out different distros and other stuff (which I usually manage to break by fiddling too much). It's been very happy running 13.10 32 bit (apart from Nvidia graphics, but that's another story) so I thought I'd try a new clean install of 14.04 as I've been very very happy with it running on a Lenovo X61. The 64 bit version installs fine on the Dell, works fine (apart from the Broadcom wireless but that's in a different post here). The only odd thing is, it won't shut down cleanly. The shutdown process works, the hard drive spins down and to all intents and purposes the machine is off (no mouse, keyboard etc) but I'm left with the Ubuntu logo on the screen and that's it, for hours. The I have to keep the on button pressed to reset. I thought it was a 14.04 issue, but I went back and did a clean install of 64 bit 13.10, same problem. If I do a clean install of 32 bit 13.10, it shuts down fine. It's not a big issue, just annoying and I don't like problems I can't solve. Any suggestions?

Ta!

Dean