The problem disappeared after installing  ubuntu15.10
I am periodically getting a completely frozen display during pointing and clicking using the touchpad. Mouse and keyboard become unavailable. I can easily unfreeze using Ctrl-Alt-F2 and then back with Ctrl-Alt-F7 and continue working like nothing happened.  Also, the pointer of the mouse jumps unexpectedly to the edge of the screen from time to time. This does has not happened yet while using an external USB mouse. I have not installed the DELL drivers for ubuntu yet, it seems the kernels don't match and I am hesitating (I have  3.13.0-24 but I have 3.13.0-73). The ubuntu installation was done from a usb stick on a Latitude with Windows 7 preinstalled. Windows have been wiped out and Ubuntu is the only OS on the disk. > uname -aLinux kna5 3.13.0-73-generic #116-Ubuntu SMP Fri Dec 4 15:31:30 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux 
Latitude 3550: Touchpad freezes display on Ubuntu 14.04