I know this is an old thread, but I've a couple of comments:

First, Apple's Disk Utility locks out some options if it doesn't see 128MB or more free space after certain partitions. It's conceivable that your NTFS partition didn't have sufficient free space after it, or it was placed too close after your HFS+ partition, and so this was causing at least some of the problems.

Second, gParted probably either converted a hybrid MBR to a conventional GPT or changed the GPT data structures without modifying the MBR. It also may have wiped the boot loader out of the MBR. Converting to a straight-GPT setup would at least leave you with a good GPT, and it would theoretically be possible to create a fresh hybrid MBR and/or re-install the boot loader. Actually doing those things would involve jumping through some hoops; others have mentioned some of the hoops. Changing the GPT structures but not the MBR structures, OTOH, would leave the disk in a dangerously contradictory state -- the two partition tables wouldn't agree with one another and so different OSes and utilities could see the disk in different ways, potentially leading to very serious damage. At this point there's no way of knowing for sure what really happened.

Finally, my GPT fdisk program includes options to repair various types of damage, but real-world testing of those features is scant. It's too late for you now, but if somebody with a similar problem would care to test GPT fdisk, I'd appreciate hearing how it goes. Be cautious, though -- as I said, real-world testing of GPT fdisk's error-recovery options has been limited. These options are also intended for people who know what they're doing. At a minimum, anybody attempting such data recovery should read the Wikipedia entry on GPT to provide some background on GPT layout. That done, start with the 'v' (verify) option to check for damage. That done, reloading the primary or backup partition table or rebuilding the protective MBR might be in order; what would work best depends on the damage.