Game start problem, cannot solve

[JEM16]

I got a beta code yesterday and tried to start the game, but I was missing a .dll. I downloaded it, updated java, and the game worked. I played for a couple hours then quit and went to help my brother get the game. He was not able to get past the initial client download without it quitting or freezing. I tried to help for about an hour then gave up for the day and went to play on my computer. I hadn't left the character select screen and everything was going fine for about an hour, when the game suddenly crashed (a little popup in the corner told me some error had occurred). I then tried to start the game and java just quits.

For maybe 5 hours yesterday and 3 hours today I've been trying to solve this, to no avail. I've read at least a dozen threads on this forum and the Paradox forum with similar problems. I've tried every solution that I've seen including: updating java, downgrading to java 6, clearing caches, deleting temporary files, making sure java and salem are completely removed and reinstalling them both, trying Ender's client, waiting for 20+ minutes for the download to unfreeze, checked router and ports.

I'm out of ideas or i would not have posted yet another thread about this problem. Specifically my problem is both the java web start download (or whatever it's called) freezing at like 90%, or when it does finish, immediately getting a message that java se has stopped working. I've redownloaded, and reinstalled things countless times and I'm just exasperated at this point. The really annoying part is how it worked at first. Help would be extremely appreciated.

Vista 32 SP2
Intel Core2 DuoT8300@2.40Ghz
3Gb RAM
Java 7u13 or Java 6u39 (i've tried both)

[MagicManICT]

I've been thinking on this for a bit, and I'm not entirely sure what the problem could be. The only thing I haven't seen you mention is working out if the network could be at fault. If there's errors in communication, it could work just fine one minute, hour, or day, and the next quit all together. Is your brother on the same network you're on? If so, it points in this direction even more.