I use a rooted phone and Link2SD app to move/freeze apps etc.A couple of times on my S5830i Galaxy Ace I've had the fault call where is cannot mount the scripts.
I've found a solution that works for me every time whereas other solutions on the net failed me
Instead of using Mini Partition Tool as per many posts you will find on this subject I used my other free Partition Manager as it seems to like SD cards better,
EaseUS Partition Manager(Free version),
Use the same instructions found in posts but use this software but don't take shortcuts e.g once you have partitioned and formatted the card let the program update it's operations in it's screen and then also un-mount the SD from the PC the proper way by software"Ejecting" it using the eject option in Windows Explorer and right clicking on the SD card/eject and then physically remove the card.
Once inserted in the Phone you may have to reboot the phone after the SD card has been read and you have chosen the correct setting/extension you have used and even if the fault call does or does not occur back in Link2SD.Link2SD has the option the reboot(It reboots the O/S).
HTH
Note:I have used their free software for years and keep disk image backups of my Dual Boot WinXP/Win7 systems on my Hard drive/s using their free,"ToDo" backup software.
I've found a solution that works for me every time whereas other solutions on the net failed me

Instead of using Mini Partition Tool as per many posts you will find on this subject I used my other free Partition Manager as it seems to like SD cards better,
EaseUS Partition Manager(Free version),
Use the same instructions found in posts but use this software but don't take shortcuts e.g once you have partitioned and formatted the card let the program update it's operations in it's screen and then also un-mount the SD from the PC the proper way by software"Ejecting" it using the eject option in Windows Explorer and right clicking on the SD card/eject and then physically remove the card.
Once inserted in the Phone you may have to reboot the phone after the SD card has been read and you have chosen the correct setting/extension you have used and even if the fault call does or does not occur back in Link2SD.Link2SD has the option the reboot(It reboots the O/S).
HTH

Note:I have used their free software for years and keep disk image backups of my Dual Boot WinXP/Win7 systems on my Hard drive/s using their free,"ToDo" backup software.