Configuration: OS X 10.9.1 / macbook pro / digiKam 3.5.0 (up-to-date macports)
After using Full Screen mode and then quitting digiKam, every time digiKam is run again it apparently starts correctly all the way up to displaying its window but when you try to view an album it hangs (beachball of death) and has to be force killed. This behaviour disappears if you remove digikamrc or replace it by a version from before Full Screen mode was used. Thus it appears that something which is saved in digikamrc when digiKam exits after using Full Screen mode causes the subsequent problems.
(The hang symptom appears to be very similar to that reported in bug #325112.)

Reproducible: Always

Steps to Reproduce:
1. Prepare a clean starting configuration (this not obligatory, but rules out initial corrupt files as possible sources of problems):
Move ~/Library/Preferences/KDE/share/config/digikamrc somewhere (e.g. to the Desktop)
Make a directory containing one jpeg and nothing else, for example ~/testpictures
2. Run digiKam. The configuration wizard starts automatically.
3. Set images and metadata to be stored in ~/testpictures
4. Accept the defaults for the rest of the configuration wizard settings
5. In the digiKam window, click on Full Screen to go to Full Screen mode
6. Quit digiKam
7. Run digiKam
8. In the "My Albums" panel, click on /Users/yourusername/testpictures
Actual Results:  
DigiKam hangs (bbod), without displaying the thumbnail of the jpeg which is in ~/testpictures.

Expected Results:  
DigiKam should display the thumbnail view (one image) of ~/testpictures.

The first time digiKam runs you can click around in it, displaying the ~/testpictures album, previewing the image and so on, both before and after using Full Screen mode. The problem only appears after quitting and restarting digiKam. If you quit digiKam while it is displaying the thumbnail view of the album, the next time it starts it will attempt to re-display it and will therefore hang all by itself. It makes no difference if you quit digiKam while in Full Screen mode (as in step 6), or if you leave Full Screen mode before quitting digiKam. If you carry out this exercise using a pre-existing album directory containing many pictures and a good database, the behaviour is the same.
As I said above, the problem goes away if one removes digikamrc again, without changing anything in the image directory. 
(I have not mentioned explicitly above that when digiKam starts you have to quit "Tip of the day". If digiKam hangs itself because its initial display is an album thumbnail view, you cannot quit tip of the day.)