Check theose backlight timeout settings in the Screen/Keyboard settings. There is also an option to auto dim the backlight according to the surrounding light. If all else fails a Battery pull or a wipe (with a backup first, of course) might be in order.
When this happened to my storm, I had to take it in and they had to replace it! I am on my 3rd storm. Not fair to say becuase my 1st one got stolen so I am on my 2nd!
i'm actually having a similar but different problem. Installed .191 last night and everything works great only problem is everytime i switch to landscape the light dims. when i switch back to portrait it brightens up again. it's really annoying! Is there anyway to fix this?