This problem does also affect me.
After upgrading Ubuntu 12.04 -> 14.04 I also experience freeze after waking up my laptop from suspend. The only way to login is to reboot the machine. Restarting lightdm doesn't help.
I use the nouveau-driver.
Hardware-specs: http://support.lenovo.com/en_DK/landing.page?qpq=6458-AT7
This problem does also affect me.
After upgrading Ubuntu 12.04 -> 14.04 I also experience freeze after waking up my laptop from suspend. The only way to login is to reboot the machine. Restarting lightdm doesn't help.
I use the nouveau-driver.
Hardware-specs: http:// support. lenovo. com/en_ DK/landing. page?qpq= 6458-AT7