yes !!! Deff. recommend you update to 4.1 if yu can because it can be an untether jailbreak if you upgrade it to 4.2.1 like they say you can still jailbreak only problem is you have to use redsnow and it will be a thither jailbreak meaning you need a comp. with redsnow to restart the phone. im currently on iphone4 4.2.1 jailbreak : got facetime over 3g and wifi sync . :)
Thats the problem with these jail break phones. They will work for while then quit. It is odd why you stopped being able to load Facebook. Upgading Facebook may work and there is no way to tell if it will harm the jail break that has been dome.