Hi Marc,
I opened the first shot (the sign with sun in the background). Your camera AF area is set to multi segment, which means that is reading the entire screen and then choosing what it thinks is the best available exposure settings. What is killing that shot is the bright sun in the background, the camera reads that and says whoa buddy! way to bright, gotta underexpose to compensate.
That situation is about as hard as it gets to get a well balanced exposure.
Think you need to spend a bit more time with the good book (owners manual). A camera like the K20D does not guarantee better shots than a Point & Shoot compact, which will automatically make all sorts of instant adjustments to produce an ok to good image. DSLR's give you (generic term
perator/photographer) the opportunity to move your photography up a level or two, they don't do it for you.
With a bit of homework and understanding your tool (the camera), and the principles of light/exposure you'll be taking great shots in no time.
Cheers
Grant
PS: also had a look at No 356, and much the same story. Although you have used spot metering, it depends on what 'spot' you focussed on, large black blobs on white surfaces are going to test the AF. In this shot you could have used flash.