Ubuntu 14.04 frequent mouse freeze
Solution 1:
I get it occasionally in 12.04 LTS. control+ALT+t will usually open a terminal window. modprobe -r psmouse followed by modprobe psmouse will usually fix it.
Check RAM by booting into GRUB. Boot holding shift down, then test memory.
Solution 2:
Reinstall the mouse driver :
sudo apt-get --reinstall install xserver-xorg-input-mouse