J'ai trouvé la solution (merci le net). Je la poste car après d'assez longues recherches, notamment sur http://www.camcorderinfo.com, j'ai constaté que beaucoup de monde était touché par ce problème.
Le service pack 2 de Xp était en cause. J'ai remis les drivers du SP1 et tout fonctionne désormais.
Voici la procédure que j'ai suivie:
"My solution was to copy the old Windows XP SP1 1394 drivers (dated 8-29-2002) back to the \windows\system32\drivers directory. The three drivers are; 1394bus.sys, arp1394.sys and ohci1394.sys. You may want to copy the current drivers (dated 8-4-2004) to a temporary location should you want to restore them later. I found the current drivers were also located at \windows\Driver Cache\i386\sp2.cab. From explorer, double-click on \windows\Driver Cache\i386\sp1.cab to display the contents. Highlight the three drivers listed above, right-click and "extract". Extract them to the \windows\system32\drivers folder and then restart."
(http://www.camcorderinfo.com/bbs/t106716.html)