I have a guide for you guys, maybe this will help you stop getting (or if you can't enter on your character .. getting this error)
1st: Run your Silkroad :
Step 2: When the SRO_Client appears, double click on silkerrsender and you will get Input Param Error (1):
Step 3: Enter your Account / password & Connect.
Step 4: Select your character and Press start
Step 5 : When that thing is loading after you press start, when its done, press V everybody will dissapear around you, so you will not get the error.
NOTE: IF YOU STILL GET THE ERROR (Imput Param Error (4) ) DO NOT PRESS OK! LET IT THERE AND TRY AGAIN WITH MY GUIDE!
This thing worked for me as well every time, maybe i helped you.
Respect.