The problem is not the card or the amount of space on it. The problem is that HotSynch is not working.
Advice to me from TomTom that worked was as follows:-
Please download and install free version of "Card Export" to install the maps at
http://www.softick.com/cardexport2/
1.Install and synchronise "card export".
2.Insert the Map cd in the PC drive
3.Accept the licence agreement
4.Select" palm powered"
5.Add maps
6.Select the map to install
7.Select other location
8.Storage card reader(CF,SD,MMC)