I've had simmilar problems with a two laptops and one which have not had this problem.
The problem for me was that everything seemed to freeze when i tired to use the login screen, nothing on-screen responend, execpt that i could move the mouse.
Switching to CLI worked without problems, I could log in and check if there was any 'runaway' or dead processes, there where none.
Restarting mdm had no effect, it would freeze the same way.
All the machines used the 64bit version of mint 15 with the 3.8.0-19-generic kernel. (MATE version, all of them, can't stand cinnamon)
All the computers I had that had this problem all had some flavor of the intel hd graphics adapter as the only adaptor (A lenovo x220, A HP Elitebook 8440p) while the one that didn't (Lenovo W530) is switchable between nvidia and intel.
The 32bit version of mint 13 did not have this problem on the lenovo x220 (however my W530 did suffer from
http://forums.linuxmint.com/viewtopic.p ... 54&start=0 which is extremly simmilar to this problem, but i don't get the xio syslog with this problem, if you do check this out)
I did some quick research but didn't find much (syslog didn't say anything strange, and concluded the problem was with mdm and/or with the intel drivers, when it's not paired with 3rd party gfx.
Unfortunatly none of the computers still have the configuration causing this problem, since i noticed this when trying out which dist worked best on these laptops.
The W530 does not trigger this problem, no matter if i completly disable the nvidia card or just run only on the intel drivers.
I reverted back to mint 13 on the x220 and the hp is running win xp (work laptop, now running legacy prog's)
I created my account for this post, in case someone else has these problems and this helps them any.