My first post too. I have also had the steering lock fault come up. The red one! However, I can start E60 520D just fine. The fault came up 4 days ago now and comes on every time. I have driven it about 200 miles and had no problems. I took it into a very good local garage and they put the BMW diagnostics kit on it and there was no fault. Tried other diagnostics equipment as well and ......no fault. Taking the car back in a few days as they want to check the wiring to investigate why the error came up.
Is this a case of software upgrade? I haven't had the steering 'lock' on me at all and have probably done 20 trips with no problems.