Mmc card shows write protected

hi everyone ,
i have 4 mmc card with me. 2 came with nokia and my PDA.
2 i brought from market . 2 which came with mobiles used to work only when mobiles are connected to my comp and rest 2 i can use anytime . but when i inserted remaning 2 card inside my mobiles and transfer data to to them. and when i removed it and try to run it on my memeory card reader it shows " CARD IS WRITE PROTECTED , DISABLE WRITE PROTECTION " . the card is not write protected . they contain no switch to lock the card , nor the memory card reader.
what has happned to those card why it always shows write protected cany anyone help me .

i am using winxp service pack 2
usb 2.0 card , zinx 2.0 memory card reader.