If you have not found a fix, try tapping the x key when the problem occurs.  This was suggested in answer to a problem I had of similar nature in thread, Will not open.

Yes, the x key allows me to proceed when the video problem arises :-)  Thanks.

Will give X a try next time.

Just for information sake:  On the video problem I was searching through the forum and found a suggestion concerning another problem that seems to help my problem of all blocks disappearing.

The suggestion was to tap F12 three times.  I tried this before starting my game and if allowed me to play MUCH longer before the video problem appeared.  (Maybe 2 hours play before to 4-5 hours now.)  I also found that after the problem did arise that if I cycled through the F12 series twice the problem disappeared and I could continue to play.

Thought I'd post this in case others ran into the problem.

I found it very frustrating due to the fact that I am working a long way away from the start point of the game.

Thanks much, will see what I can find.

Just for informational purposes:  Had played game several times since video drivers had been updated.  Reverted to Java 7 and all is well.  This is on an all in one computer with cheap graphics - I was surprised the game ran on it at all when first downloading the game.

Thanks for all your work!  I've spent too much time with the game but have enjoyed it greatly.

Have been using Mythruna on my pc for months - today the first screen opens, I click okay and nothing happens.  Had a java update yesterday, do not know if that is the problem.

error-1442176614397.log is new, contents below:

Uncaught exception from thread:Thread[LWJGL Renderer Thread,5,main]
org.lwjgl.LWJGLException: Pixel format not accelerated
   at org.lwjgl.opengl.WindowsPeerInfo.nChoosePixelFormat(Native Method)
   at org.lwjgl.opengl.WindowsPeerInfo.choosePixelFormat(WindowsPeerInfo.java:52)
   at org.lwjgl.opengl.WindowsDisplay.createWindow(WindowsDisplay.java:210)
   at org.lwjgl.opengl.Display.createWindow(Display.java:306)
   at org.lwjgl.opengl.Display.create(Display.java:873)
   at org.lwjgl.opengl.Display.create(Display.java:782)
   at com.jme3.system.lwjgl.LwjglDisplay.createContext(LwjglDisplay.java:137)
   at com.jme3.system.lwjgl.LwjglAbstractDisplay.initInThread(LwjglAbstractDisplay.java:113)
   at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:205)
   at java.lang.Thread.run(Unknown Source)
Application was not initialized.

Also, after deleting blocks for a long time the video goes funny, looks like you are seeing underlying structure instead of the blocks.  Wait a few seconds and blocks reappear but if you continue deleting the same thing happens.  Continue the cycle and it locks up - when you go to the exit screen is blank - if you move cursor and listen to the drum beat you can close it.