Problem: The launcher is saying "port is in uuse"
The game has failed to shut down properly, open task manager and force the game to close, then retry.

Problem: My character's stats are decreasing after each login
You changed your profile's XP rate to way higher than what is supported. Maximum supported XP rate is 5.0 for normal players and 10.0 for Hardcore Ironman players. There are no plans to change the maximum supported XP rates in the future.

Problem: The console log keeps repeating "Still waiting for the server to start..."
You have extracted the files to a path containing spaces, e.g.: C:\Users\My Name\Documents\2009scape. Move the directory someplace else where there's no spaces in the path.

Problem: The MySQL server says "bin\mysqld.exe: Can't change dir to '<path>' (Errcode: 2 "No such file or directory")
Update to the latest singleplayer, which no longer uses an SQL database.