via http://psp.dashhacks.com/2012/04/24/...-660-me-beta-2

If you enjoyed pulling out your PSP to use neur0n's 6.60 ME custom firmware with TimeMachine, he has bought another update for you to go back.
The new Beta 2 update allows you to now install the official and debug versions of 6.60 to your memory stick, to use with TimeMachine. On top of that, a modified version of Dark Alex's Despertar Cementerio has also been released. The new version being dubbed "DCv9" gives users a choice of installing 6.60 ME or 6.60 official firmware.
You can pick up the latest version of the custom firmware modified for Time Machine below. You just need a PSP that can use a Pandora Battery. It has been found that neur0n's addon is a standalone version, so this all that needs to be installed.

http://www.sendspace.com/file/ms7fdu