companies donot give replacements unless u bought it their, normally, requiring a reciept. its sound like your bulb(lamp), is bad. the ballast often fails in cfl's. you said u borrowed it, ud be best to try a diffrent lamp(to make sure the voltage and wiring are good, try to use a cfl to check it, sometime, a weak nuetral, will fire an incadescent, but not a cfl. im possitive its the lamp tho, id hurry up and buy another one. you dont want to do irreversable damage to the plant by neglecting it. cfl's, like all flourescents, are not dimmable. you cannot dim them with out a 100 dollar reohstat,lol, so thats not the case.
id recomend a 65 watt, 5000k for the sheild at the top, and id consider hanging some 13w and 26w t-2 cool spectrum, pendelum style aronud the plant. you will need a fan for temp control tho. if your serious about the hobby, id just drop 20-50 bucks on some lamps and holders, still makes it a cheap hobby....lol...
i wish you good luck, and ill watch for your posts.......