Media File Is Collapsed Or Unavailable - E-8302: Cannot Play Track (C658) - UPDATED - Potential issue with CDJ Case Sensitive Library

0) Have you read the "READ ME FIRST" thread in its entirety AND TRIED THE SOLUTIONS THERE before posting: Yes, I swear it!
1) Operating System: Windows 7 Ultimate
2) OS Type: 64bit
3) rekordbox version: (if rekordbox can run, post the version and revision number found under Help > About) 3.3.0 rev.4268-5192
4) Using LINK: Yes
4b) LINK Connection method: DJM2000 / Direct
4c) Using with CDJs: Yes - CDJ2000NXS 1.24
5) Source Hard drive - Internal NTFS & USB FAT32
5b) Connection type; USB2.0
5c) Does the device have multiple partitions: No
5d) If it's a flash drive, is it a U3 device: N/A
5e) With what utility did you format the device: HP USB Formatting Utility
6) Export Hard drive / Flash drive / SD card file system: FAT32
6b) Connection type: USB2.0
6c) Does the device have multiple partitions: No
6d) If it's a flash drive, is it a U3 device: N/A
6e) With what utility did you format the device: HP USB Formatting Utility
7) Have you scanned your files for errors: Yes
7b) Have you scanned your drive for errors: Yes
8) Is rekordbox crashing at all: No
8a) If crashing, is it resulting in: an error message OR a crash log OR both (DO NOT POST YOUR CRASH LOG UNLESS REQUESTED!)
8b) If not crashing, are there any error messages: Yes - on CDJ "E-8302: Cannot play track (C658)
9) Are you able to repeat / reproduce the problem: Yes
9a) If yes, can you do it consistently: Yes
10) Does the problem occur with one specific song: No
10a) If yes, please post a link to it:
11) Any other notes regarding your setup only:
12) Provide as much detail of the issue here:

OK.
So - I have scoured the forums - and this issue is potentially caused by my built in Realtek Network Controller - (which I have updated to the latest firmware) - I have ordered a USB NIC - I will try this when It arrives and update.

This is my scenario...

I have my full music collection on my external drive.
If I plug the external drive directly into the CDJ - it can read and load playlists correctly. Win.
If I plug the external drive into the PC, I can access all the tracks via Rekordbox, they all play perfectly.

BUT.

When I use LINK function - accessing any tracks via the CDJ LINK, which are stored on the external device, either via playlists, or drag and drop (from collection node - NOT device node) - I generate this error message.

Media File Is Collapsed Or Unavailable - E-8302: Cannot Play Track (C658)

I know my LINK function is working because - I added a number of tracks stored on the PC internal hard drive to Rekordbox Collection - these play perfectly fine. I then choose a track on the External device and ERROR rears it ugly head...

My Windows firewall is setup correctly - see above - Link is working!!
My Antivirus (Microsoft Security Essentials) is off.
I have turned off network sharing.

OK.

I did another little test.

I re-imported a couple of tracks from the external drive.

I can play them on the device. WIN?! No - now I have duplicates.

The difference I can see is that the ones I CAN play have a capital M:\

The ones I CANNOT play have a lowercase m:\

What's this all aboot then?!

Has the CDJ gone all case sensitive on us?!

I will explain my full process so others can understand my issue (and maybe I can work it out too!)

First I use Media Monkey to organise / Tag / Generate playlists on a Desktop PC with the full library of music on it (E:).
This then outputs to iTunes with a simple plugin and generates my external hard drive full of music (M:), and fills iTunes with the playlists made in Media Monkey. (this maybe where the case gets made small - I will check tomorrow)
Rekordbox Imports / Bridges from iTunes which points towards the external drive (M:) rather than the Desktop internal (C:).
Rekordbox places the database files upon the external drive (M:) so it can be portable.
I now want to use a laptop on LINK and the external drive at gigs - this gives me greater control over playlists and amending any issues on the fly.

I will make this work, I know it is complicated, but this is how it needs to be. End of!

Thanks for getting this far, I hope we have gotten to the bottom of a problem - Case Sensitivity perhaps!?!