Long pause after login screen on Mountain Lion

Here's some strange behaviour I noticed on a quite fresh and clean install of Mountain Lion:

There's a long pause (around 10 sec) after I type my password in the login screen until the Desktop is actually shown. The funny part is: if I hit the key for Mission Control during that pause, the I'm able to see the Desktop and interact with it, while the login screen is moved to the side. The Finder is fully usable but as soon as I start an application, the login screen moves back in and covers all until finally the login animation is displayed.

I never experienced that behaviour before and always had the whole boot process in less than 15 secs. Now it takes up to 30 secs until I see the desktop.

I already tried a lot (HardDisk Utility, permissions, LaunchAgents, LaunchDemons, StartupItems etc) with no luck. Theres nothing in the Konsole for this pause.

Any ideas? My world won't crumble about this but I'm curious what might cause this delay.

Thanks in advance,

Arroyodorado