Avast says (often) Trojen blocked, (Win32:Small.NNE) Help please!, what do I do?

Avast! says “Trojen downloader was blocked”, (Win32:Small.NNE) and sometimes (Url:Mal)…and another too fast to see, in alert box
this below is a link to a picture of the warning
http://sphotos-b.xx.fbcdn.net/hphotos-snc7/417381_497284643616906_93941884_n.jpg

I see other having the same problem, but wonder
if I have to get real technical,
or can it be explained to me,
(sorry I am so wordy…so curious, for an answer, I can understand)

What do I do?

It happens ever 10 min. or so. or when I turn on browser, (chrome).
Do I:
Not worry about it, it is blocked?
Read another answer, and do that… without understanding if I am infected or not…and if all the hassle is worth it?
Do a system restore to yesturday, or further?..

…because: they just have my computers address …and it will keep trying,
to plant a trojen downloader (Win32:Small.NNE), or does something reside on my browser/computer, to get rid of
What do I do… is it something I am now doing on chrome?
“Adaware” and “windows defender” detects nothing, in my main files…

Run a boot-time scan with avast and let us know if something is detected.
Do you also have the problem with another browser? e.g. Opera
The link to the picture is not working b.t.w.

hey i also suggest you follow this guide as well and attach your logs.

http://forum.avast.com/index.php?topic=53253.0

good luck