3D clouds becomes 2D ??

Hi,I can not get rid of a strange video related issue with clouds in FS2004.When passing inside a cloud, it loose horizontal thickness at all in spot plane view as if my plan is just braeking through a thin paper. With cockpit view, visibility is reduced gradually by clouds texture as I approach and pass through the clouds.I tried many setting but unable to detect the cause of it. I use;FSUIPC 3.07 ... same result even removedFPS fix ver.2 ... alternative clouds texture. same happens with default txture.100% 3D clouds ... in FS display settingFSmeteo 6.3 .... same result with FS default weather.My hardware is;Athlon XP 2200+ATI Radeon 9500pro w/latest Omega driver based on cat.3.7 ... genuin ATI driver gave me same problem512MB PC2100 DDR RAMAppreciate any helpYuki