ContentMap is not compatible with Joomla 1.7. You should upgrade to Joomla 2.5 to get ContentMap working. Don't worry, upgrade from Joomla 1.7 to 2.5 is easy.
Regardless of ContentMap, I strongly encourage you to immediately upgrade to Joomla 2.5, since Joomla 1.7 it affected by a severe security hole
and your website may be almost certainly hacked within a few days.