i've read that low humidity causes problems sticking to glass.. I have a screen cage and mist heavy 2-3 times a day, but have a glass terrarrium on the xmas wish list so if I get it I'll be able to try that out..

Maybe put more "stuff" in the cage so your geckos climb on that instead of trying to climb on the glass? I know mine love hiding in their gobs of fake leafy vines I picked up from wal-mart that I have suspended throughout various heights in their home.