How to get rid of "effects" in X?

[ansiktsburk]

All of a sudden I see a lot of anoying features in X.
When minimizing windows, they does not just disappear, but you can see them shrink and when clicking on the list of applications, you see them grow back to their original size.
ALT+TAB shows a box with small icons of all the windows that are open, ALT+SHIFT+TAB does not work any more.

What is this that my ubuntu has got infected by? A virus?
How can I get rid of it?

[polki@mac.com]

Sounds like compiz. Hit alt + f2 and type in

metacity --replace

I hope it works for you.

[Shark_AtK12]

Compiz it would be.