Hay guys, I got a problem trying to use a SDCard, its mounted on the laptop
using a USB card reader, and has worked before! now i can do a
thing :-( Bellow is the fdsik command i ran and bellow _that_ is all the
kernel errors that appeard in the syslog. I think im having problems with the
partition table (which is why i ran fdisk) but i dont know enought about
fdisk to do anything about it. Can anyone help me out here?

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stuart@polly:~$ sudo fdisk /dev/sdb
Password:

Unable to read /dev/sdb

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Aug 12 21:09:42 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:42 localhost kernel: Current sdb: sense key Medium Error
Aug 12 21:09:42 localhost kernel: end_request: I/O error, dev sdb, sector 0
Aug 12 21:09:42 localhost kernel: Buffer I/O error on device sdb, logical
block 0
Aug 12 21:09:43 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:43 localhost kernel: Info fld=0x8000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:43 localhost kernel: end_request: I/O error, dev sdb, sector 8
Aug 12 21:09:43 localhost kernel: Buffer I/O error on device sdb, logical
block 1
Aug 12 21:09:44 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:44 localhost kernel: Info fld=0x10000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:44 localhost kernel: end_request: I/O error, dev sdb, sector 16
Aug 12 21:09:44 localhost kernel: Buffer I/O error on device sdb, logical
block 2
Aug 12 21:09:45 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:45 localhost kernel: Info fld=0x18000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:45 localhost kernel: end_request: I/O error, dev sdb, sector 24
Aug 12 21:09:45 localhost kernel: Buffer I/O error on device sdb, logical
block 3
Aug 12 21:09:46 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:46 localhost kernel: Info fld=0x20000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:46 localhost kernel: end_request: I/O error, dev sdb, sector 32
Aug 12 21:09:46 localhost kernel: Buffer I/O error on device sdb, logical
block 4
Aug 12 21:09:46 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:46 localhost kernel: Info fld=0x28000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:46 localhost kernel: end_request: I/O error, dev sdb, sector 40
Aug 12 21:09:46 localhost kernel: Buffer I/O error on device sdb, logical
block 5
Aug 12 21:09:47 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:47 localhost kernel: Info fld=0x30000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:47 localhost kernel: end_request: I/O error, dev sdb, sector 48
Aug 12 21:09:47 localhost kernel: Buffer I/O error on device sdb, logical
block 6
Aug 12 21:09:48 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:48 localhost kernel: Info fld=0x38000000 (nonstd), Current sdb:
sense key Medium Error
Aug 12 21:09:48 localhost kernel: end_request: I/O error, dev sdb, sector 56
Aug 12 21:09:48 localhost kernel: Buffer I/O error on device sdb, logical
block 7
Aug 12 21:09:53 localhost kernel: SCSI error : <5 0 0 1> return code =
0x8000002
Aug 12 21:09:53 localhost kernel: Current sdb: sense key Medium Error
Aug 12 21:09:53 localhost kernel: end_request: I/O error, dev sdb, sector 0
Aug 12 21:09:53 localhost kernel: Buffer I/O error on device sdb, logical
block 0

When are those messages generated? If you unplug the reader and plug it in again is there anything useful or encouraging at the end of the output from 'dmesg'?

Maybe also the card is bad. I think this is quite common with SD cards. It's happened to me. Can you test it with other equipment?