This is happening to me too, on a Dell Latitude D510, with an Intel 915GM. The backlight level can be turned up fully and the OSD reacts correctly. However, when the display dims on idle and drops to around half brightness or less, un-idling will result in the display brightness only increasing one level instead of back to the previous level. It will properly return to the previous brightness level when plugging/unplugging AC, just not on idle.
This is happening to me too, on a Dell Latitude D510, with an Intel 915GM. The backlight level can be turned up fully and the OSD reacts correctly. However, when the display dims on idle and drops to around half brightness or less, un-idling will result in the display brightness only increasing one level instead of back to the previous level. It will properly return to the previous brightness level when plugging/unplugging AC, just not on idle.