I've been trying to get java to work in the browser for me for a long time now. And I've got two final results for you: First, it's (yet) impossible, the 64-bit java browser plugin will not be out before 2009.
But Secondly, it's possible and really easy with wine! Just download Firefox and install it. Then download Java and install it. Done! That easy! :) It should work the same way for Flash, etc.
Now finally I could use packstation.de in Linux!