Default [Q] sd unexpectedly removed

hello there , i have a problem with mY HTc chacha , i had bought kingston 8GB new memory card class 4 , and i am using link2sd to link my apps so that i could increase my internal storage , so i partationed my sd card , frist part for my songs , pics etc and i made it 7 GB ( fat 32 ) and the other one for apps (300 Mb)
at frist i made it ext3 , it works fine for a day and then it gave me error " sd unexpectedly removed " and when i restarted my phone i works well , then the same error appeared again :S so i formatted the 2d part with ext2 and tried and the same problem , finally i formatted it with fat 32 , it wokrs good for two days and then appears again , what should i do !