Where are you geologically? What kind of network connection (speed, wireless or not) do you have?

Because the black screen when you attempt to change location (e.g. jump to a party) and "Failed to Connect to the Server" point right at your network.

When exactly did you notice this issue? I would try scanning for viruses and malware. Then I would try both reinstalling the game and java. You data is stored online so you wont lose anything.

The reason why it says cannot connect to server is because it probably thinks your still logged on. Hence waiting a bit seems to fix this issue, so I dont think its network related.

If you have an ATI graphics chip, try an older driver. ATI has crappy drivers for their hardware. Im running out of things to test. Got to be missing something here.

As a last ditch effort. Run msconfig:

start--> type msconfig. Select the services tab--> there is a check box that says hid all microsoft services, click it. Then disable anything that does not pertain to your internet or graphics or steam. Move on to the start up tab and do the same here. Close and restart and try running the game.