Can't log into Skype: complains of the existence of another instance when there isn't one

Solution 1:

You can try deleting your ~/.Skype folder (remember to backup first). This usually fixes any problems of this kind.

According to sixones:

Rather than wiping the entire folder, you can close Skype and delete these files; ~/.Skype/shared.lck, ~/.Skype/username/*.lock, ~/.Skype/username/*-journal. Deleting them all clears out the lock and keeps your chat history and preferences.

You can do this by running the following command in a terminal:

rm ~/.Skype/your-username-here/shared.lck, ~/.Skype/your-username-here/.lock, ~/.Skype/your-username-here/*-journal

Where "your-username-here" is your Skype username.

You can also use the file manager to do this. Simply navigate to your ~/.Skype/your-username-here folder and delete the files manually.

Solution 2:

You can see if another skype instance is running if you type ps -ax. If you see a skype instance in the list, you could try to kill it with kill -kill XYZ. XYZ would be the pid - a most number with 4-5 digits. Good luck - maybe it works ;)