Since much people asking about "BO1" error after S4League Patch here is the fix for it,
1- Download [You must be registered and logged in to see this link.] this folder.
2- Delete the S4Client , S4Client_BE , S4Client_BE_ from your S4League folder.
3- Replace it with the files in your S4League's folder
4- Open S4_Patcher , let it update the files
5- Start the game normally
Note: This isn't a fix for the ITC ! Alexmen will update the ITC after 24 hours. Be patient!
Credit: @*-.Zer*-. (Folder link)