I have Win7 64-bit. Bought a 64GB usb 3.0 flash drive by sandisk off Amazon.

Windows will recognise it as well as the correct capacity (formatted in exFAT I believe). Whilst I can transfer files across, I can't transfer anything above a few GB (suspect 4GB limit). Given the plan was to transfer ripped films from computer to NAS (rather that go through the slow upload utility), I'm a bit miffed.

Any way around this?

Reformat the 64GB drive into NTFS or whatever Window's native format is these days?

Yep, this. 4GB is the limit for FAT so that's almost sure to be your problem, and NTFS will fix it.

Of course there's always a chance it could be a fake card. My boss bought some cheap ones off Amazon which formatted to 32GB but could only really fit about 1GB lol.

No it's fine now. Was going to format to NTFS anyway but on the sandisk forum, it advised not to. Apparently there was a faulty batch. Took the risk anyway and it seems fine so far. Just found it odd that it was formatted as exFAT.

Getting transfer speeds of around 120MB/s according to Windows.

There is a reason for using FAT on Flash.

Firstly, it's compatible with more machines. Old versions of Linux can't read NTFS for example, and that includes some routers with USB ports and Windows 98 machines.

Secondly, NTFS writes to the disk every time you read from it. It updates the "last read" flag as part of the "journal". This can wear out flash unnecessarily quickly.

Thirdly, user rights. If the files are "owned" by a user, it may be difficult to read them if you don't have admin rights. FAT doesn't have any security like that.

Incidentally, I was wrong about exFAT not supporting files over 4GB. exFAT does - it's the other older versions of FAT that don't. Perhaps your drive just wasn't formatted correctly (faulty batch you say?)
In addition, this version of FAT may not work on Linux boxes! Turns out I didn't know much about it really - I should have read the Wiki before posting

http://en.wikipedia.org/wiki/ExFAT

In all honesty, I'm really only using it to transfer files from my computer to the NAS. Trying to upload via my router takes AGES, so I figured transfer via USB3 stick (supported by both computer and NAS) would speed things up.

Yep, it sounds like it is formatted with FAT32, not exFAT.

exFAT only works with Windows Vista and Windows 7, so most devices are still formatted with FAT32, which works on XP, Linux and OS X as well as smart TVs, NAS, DVRs etc.

Edit: JJW, the "fuse-exfat" open source driver was released last week as a stable 1.0.0 release. This driver uses the FUSE framework (file system in user space), as opposed to having to bind it into the kernel.

So is it worth formatting in exFAT? I'll have a tinker later on and report back.

If both your PC and the NAS support exFAT, then it is fine, otherwise you will be better off using NTFS.