Hi all ;) READ THIS:
The problem is like that:
If your PS3 was on 4.87 and you Jailbreak it over the Xploit, you will later need to install a CFW with 4.87. BUT Rebug 4.87 is not here for now, so people´s install a CFW like Ferrox/Evilnat 4.87 but there is no Togle QA activated, that's why you later have the problem to Downgrade it...
In this case, you gonna need to wait for Rebug 4.87 or just do it like on this Video.
Best Regards
NSC
