phone restarts without hanging up

[RidleyJ329]

so im talking to my fiance while shes on her evo. i recently unlocked her and put her on the deodexed stock rom. i dont know if thats connected in any way but while were talking i no longer hear her respond to me so i hang up and wait for her to call back in case she was having any kind of signal problem. when she does call back she tells me she can hear me talking to her while her phone restarted, you know with the yellow blocks and the sprint 4g poster. thought i would share this with you guys incase it may have happened before and what possible fix there might be. as far as im aware of this is the first time its happened