I do loose visibility of ground and airport lights when in a cloud in 10.45b1. Try increasing the number of cloud-puffs in the rendering settings, at the expense of framerate, of course.
When setting limited visibility, this only affects a band below a certain altitude, so you can see far while above it, then suddently loose visual contact when you enter it.
There is a bug in that you can see the "glow" of streetlights through the clouds. I filed a bug, if you want to help, do so as well (the more reports, the sooner it gets fixed). Google X-Plane bug report form.
Good luck, Jan