iMac SD reader does not write or format or delete data - it only reads

i have 21.5" imac (intel) runs os 10.6.8, sd card reader not write. says read-only in info.
used other sd cards try - same.
used write before, few months ago, stopped writing - no deleting, no adding in anything
opened disk utility, erase, repair ... etc functions disabled - cannot format it.

used used external (usb) card reader try, works fine reading , writing
disk utility works fine sd cards connected through externer card reader.

wrong 21.5" intel imac's sd card reader?
can do...???

many thanks!

priscilla

ps: recognise many people have same problem. called mac , guided me pram reset. still not help......!!! getting quite frustrated.

 

have checked position of write lock switch on sd card? it's possible when inserting mac it's being switched on.

http://kb.sandisk.com/app/answers/detail/a_id/1102/~/memory-card-is-write-protected-or-locked

 

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