Hello, I have the same problem with Mac OS X 10.5.8 and the latest version of techniclauncher : when I click on the .jar, I have an error message too.
I have Java :
-J2SE 5.0 32 bits 1.5.0_30-b03
- Java SE 64 bits 1.6.0_26-b03-384
- J2SE 5.0 64 bits 1.5.0_30-b03
- J2SE 1.4.2 32 bits 1.4.2_22