OK, I see now. The problem is that the browser checks all entries in the download list. Few weeks ago I couldn't download a file and because of that, the icon changes to red even if the latest download finished successfully. In the same time I don't clear the download list because I want to see what I've already downloaded in order not to download the same file again.
Is it possible to have some restrictions e.g. on the timeframe, which entries should be checked for changing the Opera icon to red?
Thank you for your support.