Let's reset your registry entries for Snagit to see if that helps. Since all profiles will be deleted, right-click and export any custom profiles you will not want erased so you can import them again afterward:
I would like you to do the following.
-make sure SnagIt32.exe (and in version 9/10, also that the SnagIt editor in Task Manager) is not running
-click start-->run (or the windows key + R in Vista) and type: regedit
-browse to HKEY_CURRENT_USER\Software\TechSmith\SnagIt and delete the "SnagIt" folder.
-Restart SnagIt and allow the installation to run through
Please let me know if I can be of any further assistance.