I'm trying both Ubuntu and Windows 7. On Windows 7, I get the pop up saying it's downloading but will not move past 0%; and on Ubuntu, no pop up even opens up.
What is UAC? Sorry I'm a newbie in the truest sense =/
User Access Controls. It's the Win security feature which makes default setups deal with an intrusive popup box every time you try to open a program asking if you trust it. Javaws might require admin privileges to download and install software. If a popup box comes up when you try to run the .jnlp file, you'd want to click allow... probably not the problem.
Are you downloading at work or some other place which might have firewalls up?
It sounds like the Ubuntu installation doesn't have Java with Java Web Start on it. Try downloading an installing
https://apps.ubuntu.com/cat/applications/lucid/openjdk-6-jre/ (might need to reboot after installing) - then try launching the .jnlp downloaded from Bitminter.
Out of ideas after that. /passes on to someone else