This morning when i started the map editor to continue with my map, the terrain was all blurry and it was almost impossible to do a well detailed map with the ground looking like this. I have tried almost about everything like re-install game and gpx drivers... This is very annoying and i wonder if anyone else have the same problem or know how to fix this?

You just have to switch to your "(my) documents\My Games\Heroes of Might and Magic V\Profiles\<ProfileName>" folder and edit some settings in user.cfg:
setvar gfx_16bit_mode = 0
setvar gfx_16bit_textures = 0
setvar h5_simple_render = 0