System Information App Problem

I suggest that you log in to a different user account, and then try to open the System Information app.
If you don't already have another user account, this would be a good time to make a different user, just as a test for this issue.
Make a new user in your User & Groups pref pane.
Log out, then log back in to your new user, then try System Information. I expect it will work.
How to fix in your usual account?
Try deleting the file: com.apple.SystemProfiler.plist
You can find that file in your user folder/Library/Preferences folder
If you don't know how to get to your user/Library - on 10.7.5, click on the Go menu in the Finder, and choose Library, which will show near the middle of that Go menu when you press the Option key. Press and release the Option key a couple times - you'll see Library appear in the Go menu.
Open the Preferences, and scroll to the file that you want (there's hundreds of files in that folder.) Drag the file to the trash, then log out, log back in, or simply restart your Mac. I expect that will fix your System Information.