It sounds like you just need to update your software for Mac Lion.
To do that, go to this web site: http://bit.ly/UpztK7 Once there, choose "Mac OS" and "OS X v10.7 Lion".
Once there, click on "Software". Now click on "ImageBrowser EX 1.1.0 for Mac OS X". After accepting the required disclaimer, download the file to your desktop. After downloading, click "I Decline-, Go Back" to return to the list.
Please do the same for "CameraWindow DC 8.9.1 for Mac OS X" and "PhotoStitch 3.2.6 Updater for Mac OS X"
Now, put the CD-ROM in your computer's optical drive and cancel any installer that starts up, then begin installing the software. Please install ImageBrowser LAST to allow it to link to the other Canon software.
I hope this helps,