Comment 1 for bug 1501990

Note, the workaround does not fix the problem. Removing the .cache content (in fact I removed all of .cache also in testing, makes no difference. On user login, the same error is presented.

I will retest in due course without any peripherals attached to see if this is a factor. Currently testing with the following:
Dell XPS15 (9530) - which worked flawlessly with 14.04LTS aside from poor support for UltraHD displays.

1. HDMI external monitor
2. USB receiver for Wireless Mouse + KB
2. USB 2.0 external HDD

I have observed the same crashes without some or all of these items.
Again, not an issue with 14.04 - this seems to be a new issue.