Cheers Miskin, glad to hear it is not just me who has had this issue...and also glad to hear it may not be the All Comms.Hi Saint.V8, I'm not sure if this will make you feel better, but I have EXACTLY same problem - my left xenon bulb (my car is LHD) exploded causing same "light effects" on instrument panel. These effects disappeared when I disconnected left headlight and were gone when bulb was replaced. Since that time I am not able to connect to diagnostics neither with Allcomms nor with official dealer's testbook or other serviceman's diagnostic system (I am not sure which brand it was). I am able to connect to engine and transmission ECUs via standard OBDII tools.
I, too, randomly receive ABS/HDC/... fault that disappears after engine is turned off. Probably it is not good news, but I am afraid it is not your allcomms that is broken.
I am not a pro like you and I was not able to have this fixed for almost a year, but if I could help anyhow, just let me know. I'd be so happy to find out what the problem is.
My next step when I pluck up the courage is to remove the LCM and try again.
The LCM acts as a 'Master' on one of the diagnostic buses...similarly the Instrument Pack does too, mine behaves 100% until you turn the lights on, then it will fault out again...so I can only assume it is the LCM causing grief.
Trouble is, it is half buried under the side of the dash and will require the side of the dash to come out to gain full access.
Just got to get courage to remove the trim...I am OK with nuts bolts and washers...but trim and fiddly fasteners are not really my strong point.
Once I have taken the LCM out and check again, I'll give an update!