3gs lockscreen/backlight issue

[j7m7r7]

So here's the issue: A week ago, my jailbroken 3gs (OS 3.1) started producing a white/gray screen when the screen/backlight turned off. Thus, with the auto-lock turned on, after the set time expires, the screen turns off. On pushing the home button, i get a white/grey screen (same thing happens when I take the phone away from my head after a phone call or push the sleep/power button to manually lock it). Now, the screen still works- I can slide my finger across the bottom of the screen and you can hear it unlock. I can also hold down the sleep/power button for 3 secs and then swipe across the top of the screen and it'll power off (which is the only way, besides a hard reset, to get the screen back working again). The downside to either method is that I have to watch the phone like a hawk the entire time it's rebooting because as soon as the lock screen comes back up I have to unlock it immediately or else it goes back to sleep and on hitting the home button I'm back at the white/grey screen. Otherwise, there are no other issues--as long as I keep it from locking or going to sleep the screen works perfectly.

Here's what I've tried thus far:
1) Obviously I did a lots of hard resets (holding home + sleep/power buttons).
2) Then yesterday, i upgraded to 4.3.2 (jailbroken). To my surprise, I'm still getting the damn white/grey screen.

I have not done a straight non-jailbreak restore yet because I wanted to avoid updating the baseband, in case I ever wanted to sell my phone. However, if anybody believes that doing a straight restore would likely fix the issue, and could tell me why, I'd be open to trying it.

Any advice would be appreciated.