Reflashing 3.40 oea

Anyone know if its ok (ie possible without a guaranteed brick) to reflash a custom firmware .. example reflash a 3.40 oe-a psp with the same 3.40 oe-a custom firmware? I ask as i am now having trouble booting my images since i played around with xmb. I have been using brethrens easy theme flasher but it wouldnt let me flash my flash0 backup. so i did it through recovery mode. Returned to standard xmb but still cant boot my images (from ISO folder in root). Any help would be appreciated. I am about 1 step away from reflashing it with cfw3.40 oea....

OK my impatience has answered the question.. you CAN reflash it. All problems sorted. running images no probs now. lol