Loads of thanks for the tips. Have been working hard on the possible malware scenario, and here are the results:
Microsoft security essentials: http://fs1.directupload.net/images/141216/6uy7umxt.jpg
However, I noticed that the virus and spyware definitions were not up to date, which struck me a bit for I thought this antivirus is automatically updated...
But the most interesting result came from Avira EU-Cleaner: http://fs2.directupload.net/images/141216/3mbbuqqt.jpg
Four potentially damaging elements not discovered during the earlier searches!!! here are they: http://fs2.directupload.net/images/141216/n2vq6ecr.jpg
Finally I got rid of those Godknowswhats: http://fs1.directupload.net/images/141216/axul7vx2.jpg
And now I tried again to use google, and it worked!!!
But all in all I don't really understand what happened, and have not even the faintest idea of what those first 3 things may be, or where did they come from...
Do you have any tips?
Malwarebytes looks awfully good, sure to download it.
Update: How can somebody manage to f*** me in this way in case it had really been the work of an ill-minded fellow? How can something like that be carried out? What does the other fellow need to know about my system or anything else in order to do this? Have certain suspicions, but I can hardly believe it could be...