After the PRAM reset did you reboot the MBP and the projector?
If not, connect and power up the projector, the power up MBP.
The monitor itself could be on the way out, is there another monitor you can check it on.
Another thing you can try is a VGA cable with the DVI adapter and see if that performs better.
You can also try a different cable, since it worked fine in the past, I'm just trying to help you.
check some of these out:
I hope you can find something here, it's hard to source problems when the device(s) are not in front of you.
Let me know how this works for you,
All the best