Java problem while loading runescape private server?

so for the past day i have been trying to play Ultimate scape 2 'a runescape private server' but i keep getting the white screen with a little red cross in the top left corner, it says 'error click for details' and when i click it this comes up 'Java Plug-in 1.6.0_45
Using JRE version 1.6.0_45-b06 Java HotSpot(TM) Client VM
User home directory = C:\Documents and Settings\user
---------------------------------------...
c: clear console window
f: finalize objects on finalization queue
g: garbage collect
h: display this help message
l: dump classloader list
m: print memory usage
o: trigger logging
q: hide console
r: reload policy configuration
s: dump system and deployment properties
t: dump thread list
v: dump thread stack
x: clear classloader cache
0-5: set trace level to <n>
---------------------------------------...


load: class Client not found.
java.lang.ClassNotFoundException: Client
at sun.plugin2.applet.Applet2ClassLoader.fi... Source)
at sun.plugin2.applet.Plugin2ClassLoader.lo... Source)
at sun.plugin2.applet.Plugin2ClassLoader.lo... Source)
at sun.plugin2.applet.Plugin2ClassLoader.lo... Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.plugin2.applet.Plugin2ClassLoader.lo... Source)
at sun.plugin2.applet.Plugin2Manager.create... Source)
at sun.plugin2.applet.Plugin2Manager$Applet... Source)
at java.lang.Thread.run(Unknown Source)
Exception: java.lang.ClassNotFoundException: Client'

i dont have a clue what it means but i have tried everything under the sun to fix it, including, reinstalling java 7 several times, deleting all java and installing java 6, restarting my pc, opening the port for runescape, different browsers and a load of other things, is there a way to fix this that i havent tried? please help me, Thanks