ok.......
first, whenever I try to use the World of Minecraft client with the most recent version of minecraft.jar I get this:

autodetecting java
Testing default folder
Checking C:\Program Files\Java\jre6 folder
Found java in C:\Program Files\Java\jre6 folder
Starting java from "C:\Program Files\Java\jre6\bin\java.exe"
Exception in thread "main" java.lang.NoClassDefFoundError: com/mojang/minecraft/
MinecraftApplet
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(Unknown Source)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Caused by: java.lang.ClassNotFoundException: com.mojang.minecraft.MinecraftApple
t
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 12 more
Could not find the main class: Main.  Program will exit.
ERROR: Failed to run minecraft
JAVA6="C:\Program Files\Java\jre6\bin\java.exe"
Press any key to continue . . .

now...
minecraft.jar is in the correct place, in the LIB folder
my java version is the latest one

now if I get ANYONE saying to update java and redownload minecraft.jar into the lib folder I will call you a stupid f**k because you deserve it, because I already did.

now if I could get a straight answer from SOMEBODY, that will be greatly appreciated

(note: I do think it is the new version of minecraft.jar that is breaking your client btw)