First of all make sure that you don't have the write-lock or write-protect switch enabled on the SDCard or USB drive.
If the above is not the case, then follow these instructions:
Solution - Clear Read Only Attribute
Hit "Windows Key+R" and enter "cmd" to enter the command prompt:
Now type the following :........
I chose this because I heard a lot of stories about scams and that many providers I contacted said they can't unlock the Canadian I717s (one said "my Bell server" is down).
This method worked perfectly on my Bell I717M and should work for all I717 in Canada, I was able to insert a foreign SIMcard. This will work abroad too but remember entering CWM mode is different for I717's in other countries (at least theUS).
Step 1 - Root + CWM........
I backed up everything in the /mnt/sd_card directory thinking that some dataloss could occur for some reason but purposely left my microSDHC unbacked up thinking that "it won't touch that since it's external" and Samsung's and other manufacturers website even say this (that it won't be affected and not to worry etc).
Apparently I was wrong, my microSD was "undetected" and asked to be formatted after the upgrade (there goes 3-months worth of family photos). No........