On Tue, 19 Nov 2013 13:49:36 -0800 (PST), Calvin wrote:

It locks out at some point but then is quite happy to start again if I
press the lockout button (inside the outer cover on the burner itself).
I've been "playing" and I get the feeling that it behaves itself better
if the temperature control is set lower, although at the moment that's
just my impression.

I don't know that particular boiler but oil burners are generally bog
simple. I doubt very much that temperature control is directly
related to the lockout.

Lockouts occur when the control system in the burner thinks the flame
has gone out and after trying to reingnite it for a few seconds
thinks it hasn't succeeded. The flame detection uses a photocell and
these can get sooted up, hence the use of the word "thinks" above.
When was the burner last cleaned and serviced?

Of course you have checked that there is oil in the tank, that all
valves are properly open (don't forget the fire valve), that
filters/valves aren't blocked and that you have oil not oil/water at
the burner.

Remember oil floats on water. So water sinks in oil, to collect at
low points in the pipework. Has there been a frost? The water can
freeze in the pipes blocking or at least obstructing it. Spent half a
day getting the ice/slush out of our feed pipe a few winters back.
not nice with a foot of snow on the ground. Then another half a day
clearing all the gunge that had been dislodged out of the fire valve
and filter ... Have now dewatered the tank and have a glass bowl
filter to trap, and make visible, any water that does leave the tank
before it enters the pipework.

--
Cheers
Dave.