Eduard, I don't know how you keep stumbling upon these things but please keep it up! I for one appreciate it. I get so frustrated with adobes need to organize, sometimes I wish I could just open images and export, this constant back up library deal must be taking up a lot of hd space.
I have times after importing from the camera/card reader I can't find the images.
I had trouble with this until I documented my process and follow it to the letter every time. I create a folder on my computer's drive as well as my 2nd machine's drive with the same filename - e:\YYYY\MM.DD.YYYY - Description and then I point LR3 to the folder, and have it put the images in there. I make sure to keyword them, so if I want to find all images shot at Mill Race Park, or of Bill Smith, or whatever keyword, it's not too bad to find them.
It's amazing how many great lightroom resources there are on the web, even *free* ones! Youtube has tons of videos, Adobe has some, and I've also used kelbytraining.com and lynda.com - but it's hard to beat free!