I'm a bit sketchy on the old Carminat now, but have a dig around the forum for TMC for details. Most TMC problems relate to the fact that the TMC data isn't properly encoded on the earlier discs, and isn't there at all on some of the later ones.
Rumour had it at one point that Renault were handing out free sat-nav discs with TMC enabled. It might be worth phoning
and seeing what they have to say on the matter.
Though to be honest, having the later DVD based system with TMC, I can say that it's wrong at least as often as it's right. I'm not saying it's completely useless, but the information is far from reliable. It often diverts you around problems that cleared hours ago (or never even existed in some cases, I'm sure) and similarly tends to be pretty slow on the uptake when it comes to new problems.
If you do a lot of driving and really want useful, up to date information, then have a serious look at one of these.
eBay.co.uk: Trafficmaster YQ Traffic Alert System (item 270035171307 end time 08-Oct-06 20:00:00 BST)
I've had my YQ2 (and previously a YQ before it) for donkey's years now, and I'll hang onto it until the day that they finally kill off the old Cellnet analogue paging service that these things work on, rendering them all useless. Even the YQ units don't always get it right, but they're infinitely better than TMC.
I'm on record as saying that TMC doesn't take its data from TrafficMaster, but I've since found out that it does. I can only assume that there's either a serious delay involved in getting the data onto the TMC network, or the data from other sources (RAC road reports) creates a lot of 'false positives' where traffic at supposed trouble spots actually turns out to be flowing perfectly well.