I have created a lightmap for my geomipmapped terrain. My heightmap size for the geomipmapping implementation is of the form (2^n + 1), and the lightmap generated needs to be of the same size. Could this cause an issue in terms of texture mapping since its dimensions are not a power of two (1025x1025 rather than 1024x1024)?
Not a problem if your hardware supports NPOT textures.
See :
http://www.opengl.org/wiki/NPOT_Textures#OpenGL_2.0_and_GL_ARB_texture_non_power_of_two