After a long time in which I've been unable to use Digikam due to an unrelated crash in phonon library, I finally managed to get it to install and run today.  I get the splash screen, then the main window.  The main window shows a progress bar (apparently for scanning my albums) which completes in about 26 seconds and I get a "no active process" message.  However, at the same time (i.e. right afer the main window is shown) Digikam starts using all available CPU resources (400%) and locking memory at a very high rate, until it gets to 70-80% of system memory, then I have a few minutes of swapping in which the system is unusable, and finally memory is fully exhausted and the system terminates Digikam.  It does not matter if I close the main window after it starts to use CPU and memory, the digikam process would not disappear and continues to use resources until it gets terminated.  I don't know what is being done behind the scenes (as far as I can tell Digikam doesn't generate a log file) but in the past I've been able to use Digikam (up to 3.4.0 I believe) with the same image collection.  The issue exists in 4.2.0 and I've also tried 4.1.0 and 3.5.0 with the same result.