Problem with clouds in celestia-ed

[jworld2]

Hi. I downloaded celestia-ed and some educational activities to try them out. I open celestia-ed and go to the earth and I notice that the clouds are flashing on and off slowly. first it appears normal with clouds enabled. then it appears normal but with clouds off. I check the settings and i see that the clouds are supposed to be enabled but they keep going on and off! it's getting really annoying. can anybody please help me?