Ola Ana,
To clarify, ActivInspire version 1.6.50464 is the latest version available that will run on OS version 10.5.8. The latest ActivInspire version 1.7.58968 is not supported on 10.5.or 10.4. ActivInspire version 1.7.58968 is supported on Mac OS version 10.6, 10.7 and 10.8. If you would like to update your Mac OS to one of those versions, then you will be able to update to the latest version of ActivInspire. (case# 228253)
Hope this helps!