Playing Video on iPhone while it locked

im currently using the iphone 4 with firmware 4.3
Not to long ago, i was able to play video when my phone is locked or doing other things.
what i mean by that is...
while locked
1. i have a video running
2. i lock the phone while video is running (this cause the video to pause)
3. i then double click the home button to access the ipod controls
4. hit the play arrow and ill have the audio for the acutal video.
or while doing other things
1. i have a video running
2. i hit the home button (this cause the video to pause but phone not locked)
3. double click the home button and scroll to the left to get the ipod controls
4. hit the play arrow and ill have the audio for the acutal video.
But recently this feature does not workk anymore. the reason why i do this is because i have music video which i like to listen too, and can always jump back in the watch the ones i like. and for other video which has a lot of audio (russel peters!)
does anyone know of a fix to this? i really liked this feature but aint working for me anymore. i have to leave ipod running on my iphone and cannot lock it.
im am not sure if upgrading to the firmware of 4.3 caused this because i dont know when exactly the feature stopped.
anyhelp would be appreciated.
thanks
iPhone 4 iOS 4