I have external drive connected via USB to computer. In 2.6.25.4 when
I plug into computer works fine, and have this messages in dmesg:
usb 5-1: new high speed USB device using ehci_hcd and address 4
usb 5-1: configuration #1 chosen from 1 choice
Initializing USB Mass Storage driver...
scsi2 : SCSI emulation for USB Mass Storage devices
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
usb-storage: device found at 4
usb-storage: waiting for device to settle before scanning
scsi 2:0:0:0: Direct-Access     Initio   MHV2080BH PL     3.01 PQ: 0 ANSI: 0
usb-storage: device scan complete
Driver 'sd' needs updating - please use bus_type methods
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is off
sd 2:0:0:0: [sda] Mode Sense: 00 00 00 00
sd 2:0:0:0: [sda] Assuming drive cache: write through
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is off
sd 2:0:0:0: [sda] Mode Sense: 00 00 00 00
sd 2:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1
sd 2:0:0:0: [sda] Attached SCSI disk

Works fine:
maciek@zlom:~/kernel.org/2.6.25.4$ ntfsmount /dev/sda1 ~/mnt/ntfs/
maciek@zlom:~/kernel.org/2.6.25.4$ mount | grep fuse
fusectl on /sys/fs/fuse/connections type fusectl (rw)
/dev/sda1 on /home/maciek/mnt/ntfs type fuseblk
(rw,nosuid,nodev,default_permissions,allow_other,blksize=4096,user=maciek)

But on 2.6.26-rc* sometimes I have messages "Write protect is on", e.g.:
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is on
sd 2:0:0:0: [sda] Mode Sense: 09 50 f8 af
sd 2:0:0:0: [sda] Assuming drive cache: write through
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is off
sd 2:0:0:0: [sda] Mode Sense: 00 00 00 00
sd 2:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1
sd 2:0:0:0: [sda] Attached SCSI disk

or:
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is on
sd 2:0:0:0: [sda] Mode Sense: 09 50 f8 af
sd 2:0:0:0: [sda] Assuming drive cache: write through
sd 2:0:0:0: [sda] 156301488 512-byte hardware sectors (80026 MB)
sd 2:0:0:0: [sda] Write Protect is on
sd 2:0:0:0: [sda] Mode Sense: 09 50 f8 af
sd 2:0:0:0: [sda] Assuming drive cache: write through
 sda: sda1
sd 2:0:0:0: [sda] Attached SCSI disk

Then mount fails:
maciek@zlom:~/kernel.org/2.6.26-rc2$ ntfsmount /dev/sda1 ~/mnt/ntfs/
Error opening partition device: System plików wyłącznie do odczytu.
Failed to startup volume: System plików wyłącznie do odczytu.
Failed to mount '/dev/sda1': System plików wyłącznie do odczytu.
Mount failed.

"System plików wyłącznie do odczytu." means "filesystem readonly"

Tested on two computers PC and laptop.

Dmesg and config:
2.6.25.4: http://unixy.pl/maciek/download/kernel/2.6.25.4/
2.6.26-rc1: http://unixy.pl/maciek/download/kernel/2.6.26-rc1/
2.6.26-rc2: http://unixy.pl/maciek/download/kernel/2.6.26-rc2/

-- 
Maciej Rutecki
http://www.maciek.unixy.pl