Just some small things I've known to help fix some errors. Try them all and maybe one of them will work!
Start Menu-Local Disk-Delete .Soulsplit
Updating your java:
Click Verify Version-Click Run-If java is updated your good, if not it'll prompt you to download it.
CMD Box Error on download client?
Use the .JAR file instead of the run.bat
Try deleting your browser cache
Try using Internet explorer:
This worked when soul split was first released, if it's the last option, try it!
Will add more soultions later, hopefully one of these work, they've worked for others!