GL11.glRenderMode problem

[carolus09]

I have several lists of objects, which are rendered and which can be selected by the mouse. When there are two points in a list with exactly the same coordinates they are - of course - rendered at the same position in the scene, but when I select the point the function  call  "hits = GL11.glRenderMode(GL11.GL_RENDER);" returns -1, although it should return 2.
Is it an OpenGL problem or ist it in the implementation of the function in LWJGL?
Is there any way to select the point in this situtaion?

[carolus09]

I found the solution:
OpenGL returns a negative value, if there is a buffer overflow. Increasing the buffer size is the solution.