Unknown Error popups ; solving solution

I have had a problem of "Unknown Error" popups. It pop so often that it was very, very annoying. I came to the board for a solution, did like Riot recommanded (firewall, connection, etc). It didn't solve the problem. So I wrote directly to Riot. They sent me a link to download a Repair Tool. I used it properly, but still the problem wasn't solved.

Then I realised by myself what the problem was, and I found the solution. I'm sharing it here for you who have the same problem I had and who can't solve it.

I found out that the popups came mostly when I log in and when I browsed my friends' list. Then I noticed that 2 of my contacts in that list had weird "alien" caracters in their names. I deleted those LoL friends from the list, and problem was solved. No more "Unknown Error" popups.

That easy.