MTP errors can be linked to malfunctioning WMI services in XP.
WMI still does not work on one of my PCs, even after performing the following fixes.
Which means I have to reload XP on that system.
All hail the registry: flawed by design.
http://windowsxp.mvps.org/repairwmi.htm
http://searchwincomputing.techtarget.com/tip/0,289483,sid68_gci1160143,00.html