Upgrade to 15.10 MATE Fails - What's the Deal Here?

I am running Ubuntu MATE 15.04 on my test Lenovo T61. I went to upgrade from 15.04 to 15.10 and it blew up. I am now doing a “partial upgrade” per screen instructions. I have very little running on this laptop as it is used only for testing. This is the first time since Ver. 5.4 way back in 2006 that a Ubuntu version upgrade failed. What’s the deal here?