After I log in, sometimes (often) the screen goes black and the graphical mouse arrow appears, and it can be moved with the mouse, but nothing else happens for quite a long time (maybe a minute) and then the desktop will finally appear.
This is using Ubuntu 13.10 - AMD Phenom(tm) II X4 945 Processor × 4 - 8 GiB ram - GeForce GTX 550 Ti/PCIe/SSE2/3DNOW! - 32 bit
I have the same problem. The issue has been narrowed down by looking at /var/log/lightdm files. You will find the time at the beginning of each line in those files, so you will be able to spot the action that fails.
In x-0-greeter.log, I have something like that :
The user which causes the failure is a LDAP managed one, not a local one.
I am currently investigating...