A solution at last! This appears to be a generic problem with Windows Mobile 2003.
To solve this, download the following file, unzip and copy the CAB file to your PPC:
http://www.pc-counselor.com/bin/avantgo.arm.zip
Run the file on your PPC and when prompted if you want to overwrite files, say NO TO ALL.
After competion, resync after selecting the refresh all content in the AvntGo properties in Activesync and all should be well.
Note you may have to replace the AvantGo shortcut in IE favouries to point to avantgo://avantgo/home
Happy at last!
Ian.