Hi Folks,

Been offline for a few weeks, but done some more experimentation this week and think I have found the optimum solution.

Experimented with WMA and so here are my conclusions:
WMA-VBR 240-355kbps: tracks that exceed the 355kbps do not play.
WMA-PRO: does not recognise
WMA 192kbps (so this is the next option down from the higher quality VBR), those tracks that did not play using VBR, now play just fine.

I didn't stop there, as the 192kbps is basically the same as on my iPhone and wanted something better since the recommendations were "to be as uncompressed as possible". So tried a new tact using AAC, and that seems to work well.

Created a brand new library in iTunes just for ripping my CDs in this format (I already had my CDs ripped in Apple Lossless).
For CD import setup as follows:

AAC Encoder
Custom
Stereo Bit Rate: 320kbps
Sample Rate: Auto
Channels: Auto

Tick box for:
"use Variable Bit Rate Encoding (VBR)"

As a result of that, should see in the Details window the following:

160kbps(mono)/320kbps(stereo) VBR

Then tick the box for:
"use error correction when reading Audio CDs"

After ripping all the CDs I wanted, simply copy across the "Music" folder from within the "iTunes\iTunes Media" folder directly onto the USB stick.

So far all tracks that I had a problem with before play just fine. Interestingly I note that some of the tracks have quite high bit rates, up at 373kbps for example (similar to the WMA files that failed) and yet still play just fine. Which suggests that the system handles AAC better than WMA.

Finally, for around 2,100 tracks, consumes around 23GB on the USB stick.

So AAC seems to be the way to go to get the highest quality.

Cheers
Tom

TT