997 Navigation issues

[George36]

Spent last week touring round germany, great weather and some fantastic roads!
Day two and the Sat Nav decides to give up on me...
Luckily iPhone to the rescue so no big deal.

Anyway symptoms were as follows:

Navigation guidance would not accept a destination and it's asks me to insert Navigation CD.
It still allowed me to view the map and at around 1km scale.
Next day, same thing but map would only zoom in to about 4km scale.

Then again same thing but now it would only view the map at 10km scale.
Rest of the holiday is spent at 10km scale but it tracked my position and displayed traffic and roadwork info?

It did also reset itself a couple of times, ie powers off and PCM goes blank and reboots, plus there were times when it said MAP loading but never did complete...
Initially I thought it was the disc I was running, 08/2009 copy, but since getting home I have tried an old original 08/2007 disc and still no joy.

Since being home the PCM has rebooted a few more times and now it won't display a map at all!!!

The Navigation Status shows it's seeing Satellites, anything from 3 to 8, 2D-GPS or 3D-GPS at a distance of between 70 and 230 feet.
I've checked the connections to the DVD drive and all looks fine, MOST can be seen flashing when disconnected.

I'm not sure where the fault lies?
PCM, DVD drive, MOST cable or Navigation disc...
Anyone have any ideas or expertise in this area?

Car is a 2006 C4S

Thanks in advance

Cheers George