Strange shadow in shots

[Kronen]

I have just bought a Sony a230, but suddenly there is a weird dark shadow in the middle of some of my shots (the ones where the middle isn't either very bright or very dark).
At first I just thought it was something on the lens, but it appeared in to very distinct shapes. Either as a larger, diffuse shadow

or as a clear dark L-shape

Does anyone have an idea to what might cause this.
I appreciate any help you can give


- Kronen

[bono]

Try to clean your sensor - this could be dust or something on it. You have to be careful doing this!

[OsmosisStudios]

Yup: dust on the sensor. Use a blower (like a RocketBlower) or bring it to a camera store that's comfortable with it.

[zappo]

Yes this is sensor dust, and a pretty nasty one, too. Best google a little bit about how to remove this, there are plenty of tips around. If you don't mind spending some money bring the camera to the service.