Psp slim wont go onto xmb after using pandora

The other day I was testing my new pandora's battery and memory stick, so I used it on my friend's new psp-slim (yes I have Despertar del cementerio V3), all went fine, but for some reason after the process the psp wouldn't get into the xmb, it just hanged after the sony computer entertainment logo and just showed the waves but no icons, then it turned off after 5 seconds like it was bricked

I really got scared since this was my friend's psp and it was new and also a slim (I would have had to pay for it, and I already owe this guy 60 bucks:p)

I turned it on again and the same, then I turned it off again and for some reason I thought it would be a good Idea if I went into recovery and use the option: format flash1. So I did, it finished but when I got out of recovery I got a BSOD, I pressed "O" and all went fine again from there (I was like: pheeeewww). (was a good Idea after all)

Does anyone know, what I did wrong?, I don't want to go through all this stress with mine or my other friend's psp

I'm thinking that all went wrong because I removed the magic memory stick before turning it on again, cause in all the videos I've seen on youtube they just switch the batteries and do nothing with the memory stick (also they got no BSOD)

My other theory is that he had a higher firmware than 3.71 (I didn't check), and I remember that everytime you do a downgrade on the fat you get BSOD

Opinions anyone?