actually, u can revert back to cex. I've personally done it. what is happening is that a certain address is modified in the flash which allows u to install dex cfw. without modifying the address, u will receive "no applicable update" if u try to install dex fw since it knows ur not using a debug system. currently, there's no way to install dex fw or cex cfw without making this modification. and, u can only install one or the other at any given time. in order to revert back to cex, u have to use the original flash dump that does not contain this modification. the system will them presume ur using a retail ps3 allowing u to install cfw. aside from some of the features of the cobra dongle, there's absolutely no reason to revert back. if u don't have the cobra dongle, u might as well convert to dex, 'cause 3.55 dex has all of the options of kmeaw and much more including the ability to play about 95% of current games as backups and 100% directly from retail discs without the problem of updating that u'd have with cex cfw. also, it is strongly recommended u dehash the system before going to dex especially if u ever decide to revert back. qa flagging is probably the easiest way to do this. if u don't do this, the syscon checks that r made when installing 3.55 fw may cause rsod.