bootup hung after upgrade

[walleye2]

I had 17 running after a fresh install. I then clicked on the "upgrade to 18.04". Install went well but after rebooting several times, all I receive is the red screen with the 5 dots that go from red to white to red. this stops on the 3rd pass and never proceeds further. I am clueless on how to proceed other than returning back to 17. This is on a Dell machine. I noticed when installing 17 that is said it was doing amd64 files, which I thought incorrect although 17 seemed to work .
Thanks for any help.
Simple machine. no other os, graphics or usb devices. Intel dual core2, 8 g memory. previously ran 16.04 with no issues.