For more information:
What I believe is the reason behind the ThemePSP brickings
What Do You Call This?
What has been confirmed:
Most of the bricks are from 2.6 downgraders.
When the background is white, but the font has been modded, you're in a pre-brick stage.
The Vincent theme has given this white background to two downgraders.
We believe the 1.5 firmware, downgraded from 2.6, is not a clean firmware, we believe upgrading to 2.0 after downgrading from 2.6/2.5 then using the MPH downgrader is going to give you a clean firmware.
It has been suggested to flash 1, not 0 (default one) so if flash1 becomes corrupt, it won't be a brick, this has been suggested by a forum member and I don't know anything about this so use at your own risk.
Bricked PSPs so far:
andrewtr89 (2.6 --> 1.5 Bricked on third flash.)
Hawk (2.6 --> 1.5 Wasn't on first flash.) Vincent pre-brick
LegendOne (2.6 --> 1.5)
Resso (2.6 --> 1.5 first flash was Vincent) Vincent pre-brick
We knew there was a risk of bricking when flashing, but 1 or 2 bricks a day have been alarming for the homebrew community, just watch out.