Same things happening to me but I really don't think it's a graphics problem

Well if the game is freezing/crashing it may be due to your laptop not being able to handle the load and putting your graphics on the lowest settings and then loading the game sometimes works.

I don't know much about Java, but you could try restarting your computer because this often solves conflicting programs and processes, if you didn't know already, sometimes when you close programs and .exe files, the computer closes the application but bugs and the process is still running, meaning you think you've closed the program when in actual fact the computer is still running it even though the application isn't visible on screen.

If that doesn't work you can try allocating better performance to Spiral Knights:

Make sure you have Spiral Knights open,
Now open the Task Manager (usually accessed by Ctrl + Alt + Delete) and clicking on "Start Task Manager",
In the Applications tab, right click on Spiral Knights and click "Go To Process",
It should switch you to the "Processes" window with "javaw.exe" highlighted, Right click and hover over "Set Priority" and click on "High", you can also make sure all the available cores of your processor are working on the game by right clicking on "javaw.exe" and clicking on "Set Affinity...", and make sure the "All Processors" box is checked.

As it stands I haven't encountered this problem.... Yet, so it could just be as simple as restarting your computer or lowering your graphics or it may be the bit more technical one with the Task Manager, sorry if I seem patronising, I just presumed when making the tutorial that some of you might not be complete nerds like me and need some explanation rather than just assuming you know your way around computers. But yeah, If these don't work at all I'm sorry, I'm just handing out some of the stuff which I thought might work.

Hope this works for you ^^
Lew.

I'm, having this exact same problem. In the preview this would happens sometimes, but if I just went back and forth between the log in screen and character select it'd work eventually. Seemed to get more and more frequent the closer to the end of the preview we got. Earlier today I logged on once no problem, got to Haven, and logged off. Trying it now, I can't get in at all no matter how many times I try. The 'time played' number changes each time I go back and forth, so it's like it thinks I'm in the game but it doesn't transition away from the character select screen... My computer can run the game like a dream so that's not the problem, I never changed anything, I just don't know man. If you see a guy named 'Sahiro' popping up and disappearing over and over again that's why.

And I am in! Don't know what happened but it's working! Good way to start the day.