using chdk on sx40

I am at a standstill on using chdk on my sx40. I have the right version on the 4 gb sd card and after I start camera on play back mode, press firmware update have the chdk appears for 1 sec, I use shutter button to start record mode, the screen shows at the top the battery %, sd card volume, etc & a small white line half way across the bottom but cannot make the chdk menu appear. I have tried everything I can think of & read the chdk forums for 2 hour but to no avail. Any ideas or help would be appreciated. jimjoh