Skyseed, I fixed the problem. What I did was moving the folder "C:Users\your-user-name\AppData\Roaming\SecondLife" aside, so far the problem seems to go away.
The Roaming directory has your chat logs, that's why I moved it aside, not deleting it. The related solutions i googled before all suggested to remove AppData\Local\SecondLife. Tried that before this, didn't help.
If you are able to solve your issue this way or any other way, please comment.