Apple's Boot Camp uses a hybrid MBR to help a BIOS-booted Windows coexist with an EFI-booted OS X. As noted on the linked-to page, hybrid MBRs are dangerous and trouble-prone. I suspect you may be running into a problem related to this. Your fdisk output seems to show the MBR side of things -- certainly the single line of output you've shown is consistent with either a pure MBR disk or a hybrid MBR, not with a pure GPT disk. (Hint: Don't be stingy with program output when posting questions; show the entire output of a command like fdisk -l /dev/sdc!)
One of the problems with hybrid MBRs is that the MBR and GPT sides can get out of sync. It's entirely possible that this has happened to you -- but that's speculative on my part. To know, you'd need to compare the start and end points of the GPT and MBR partition tables. To do this, run both gdisk -l /dev/sdc (to see the GPT side) and fdisk -l /dev/sdc (to see the MBR side), and compare the data.
Another possibility is that you're not accessing the correct partition. The MBR's /dev/sdc3 (which you've identified as being a Windows partition) may not be the same as the GPT's /dev/sdc3. This is a critical point because in Linux, the GPT side is what's used to create device identifiers, so when you tried to mount /dev/sdc3, you were probably mounting the GPT's /dev/sdc3, not the MBR's /dev/sdc3. (Of course, this assumes that the disk has a hybrid MBR, which isn't certain given the information you've presented, although I think it's likely.) Again, comparing the GPT and MBR data from gdisk and fdisk, respectively, will help you understand what's going on.
