When Sony put online on firmware 6.60, developers quickly realized that the internal structure of this update has undergone some changes. Thus, when the Custom Firmware 6.60 ME was posted, it was incompatible with a significant number of plugins: popsloader, AubioBoost, PSPStates, CXMB, etc..
But fortunately, some developers are bent on re-adapt to the Must-Have Custom Firmware 6.60 ME. Frostegater, Russian developer, and put online a new version of CXMB, which is compatible with Custom Firmware 6.60 ME.
Example of unofficial theme ...
Since the Custom Firmware 3.52 M33, you can customize your XMB in-depth using unofficial themes. But these issues should be installed directly in the flash0 of the PSP, and the risk of brick was present. This problem was solved with the arrival of CXMB, a plugin to install themes unofficial converted in the form of CTF, directly from the XMB, without any risk.
However, the developer has simply added the keys to firmware 6.60 and did not attempt to create a theme compatible. It will certainly expect an update from CBC GUI Tool for adapting old themes.
CXMB for 3.71 to 6.60 v2
Download, instructions and user manual available
in the form of downloadable below.