Creating Tables with 2.5?

Okay, I am pulling my hair out. I am creating a plugin for the first time that creates two tables. The plugin works great except with WP 2.5. I can’t get it to create my tables and it is driving me crazy. I have read that you need to set your variables to global outside the function that is creating your tables. I have tried that but no luck. Not sure what I am doing wrong.

Can anyone point me to an example of creating tables within a plugin under 2.5. I am sure if I can see something I can figure out what I am doing wrong.

Cheers.