Problem with e60 intermitent wont start/ key error

Well lads just today started to have an issue with my key, turn igntion and nothing, no dash lights or anything, then eventually on an off it started an drove fine, now im gettin dash lights, starts sometimes and then while driving i get an error of a key with a line through it saying no key signal or sumthin like that, i only have 1 key for it, so cant check another, im guessing its key? But just wondrring anyone have a similar issue before? Its 2004 so has diamond key, i had same issue with an e39 before and it was the key aswell(diamond key aswell)

Don't rule out the possibility of a duff car battery. e60's can throw all sorts of odd and misleading lights, errors, etc. when the battery is on its last legs. The weather has turned a little cooler in the past few days so a sudden battery demise is not out of the question.

New battery in it only a few months back but il get it checked!

just incase anyone stumbles on this in the future it was my key that was at fault! went to locksmiths and could only read code off key the odd time, was coming and going. new key programmed and working fine now!