Thank you for the post.
Bento 4 is not compatible with OS X Leopard (10.5). The system requirements for Bento 4 can be found in KB7888:
The software update article for Bento 4.1.2 states:
"IMPORTANT: The minimum System Requirement for Bento 4.1 for Mac is OS X Snow Leopard (10.6.6)."
My suggestion would be to uninstall Bento 4.1.2 and download and install Bento 4.0.7 which is compatible with Mac OS X Leopard (10.5):