Finally, the windows update works again, at least it downloaded and installed the updates, but i still get the error code if i try a second time.
I clicked the "Check online for updates from Microsoft Update" link instead of clicking the "check for updates" button and it worked. Not sure if this link was there all the time but I don't think so.
Maybe the troubleshooter from the 2nd post did the trick.
Anyway, thanks to all for the help.
I will try to manually reset the Windows Update components with the link mentioned above and report back here the outcome.