Ok, so some of you might know what the issue is with the latest MCP. Files being not found etc.
There are some tutorials everywhere on the web but for the mpgh users here it is.

Go ahead, download the latest mcp for 1.6.4. Unzip / Extract it. Hit decompile and wait for it to finish.

After its done, go ahead and launch Eclipse and navigate to your Eclipse folder in the mcp with the decompiled source.

 
Eclipse




When you open it, it could look like this.
If you try to run the game in debug or normal mode, youd get an error of the main class not being loaded.

LETS FIX IT! Woo

Go ahead and right click the Client folder; select the Build Path > Configure Build Path.

 
Right Click




Now youre gonna get a new window popping up. Dont be scared!

Navigate your cursor carefully to the "Libraries" tab.

 
Libraries Tab




Now. See that red square with a cross in it? That's an error. We gotta deal with this little bugger.

Don't be scared to click on the "1.6.3.jar" or maybe even 1.6.4 if you're special enough.

Click on the 'errored' jar and hit edit on the right hand side.

Now. Navigate to your MCP folder. And then to the following folders.

mcp/jars/versions/1.6.4

Click on the 1.6.4.jar and click open.

 
MCP jars




Press open... Click Ok... And there you go.



EDIT: No idea what happened to few of the pictures.. the image host being spazzy.. Cutting images off -.-