dead then alive f5

hi guys.i know similar things have been covered here but dont wanna hijack anyone elses thread.the f5 just went to scrambled then completely died.after trying all the usual unplugging i guessed it must need the null modem cable and to be recovered.sorted the cable but tried the box again out of curiosity and it pinged back on straight away.then it died again and has now came back on haha my question is what can i do to recover the box and make sure it doesnt happen again now that i can get my usb back into it?i mean can i load the eromupgrade file or is that just for the box with the null modem cable?cheers in advance guys