Please make sure you check the requirements and the below issues before reporting a new one.
Also, when reporting a new issue, please attach the console text file in your [home]/Spacemen directory.
To find your home directory, please check this wiki page .

Issue: Crash without error message on 32bit OS's due to Out-of-memory exception (check console file [home]/Spacemen/console....txt)
Cause: Known java bug JDK-6296278
Solution: None at the moment, working on a workaround.

Issue: Failed to create display LWJGLException: Pixel format not accelerated.
Cause: Out-dated video adapter driver.
Solution: Please update to the newest graphic card driver from the chipset manufacturer. Stock drivers installed by MS Windows for example do not support OpenGL.

Issue: Uncaught exception thrown in Thread[LWJGL Render Tread,5,main]
RenderException: compile error in:ShaderSource[name=MatDefs/Shield.frag, defines, type=Fragment, language=GLSL100]
Cause: Out-dated video adapter driver.
Solution: Please update to the newest graphic card driver from the chipset manufacturer.

Issue: RenderException: non-power-of-2 framebuffer textures are not supported by video hardware.
Cause: "Older The R300 and R400-based cards (Radeon 9500+ and X500+) are incapable of generic NPOT usage. You can use NPOTs, but only if the texture has no mipmaps.NV30-based cards (GeForce FX of any kind) are incapable of NPOTs at all, despite implementing OpenGL 2.0 (which requires NPOT). It will do software rendering if you try to use it.All newer hardware can handle NPOTs of any kind perfectly."
Solution: None at the moment.

Issue: "Spacemen" can't be open because it is from an unidentified developer.
Cause: In alpha/beta stage the Mac version is not signed as per App Store requirements.
Solution: Workaround

Issue: Failed to create display LWJGLException: Failed to set display mode (-2).
Cause: The selected settings, screen resolution and refresh frequency, were not accepted by the LWJGL.
Solution: Please start the game with different settings, first change the frequency, then resolution and finally full-screen mode.