Hi GLF, type 1 cavalry here at last! :lol:
A few possibilities occured to me.
First, the timing of basal dose splits may be responsible for your late evening bg surge. While I don't think there's any absolute necessity to split the dose by 12 hours ( Lantus' activity profile makes it quite slow to take effect and to tail-off) it certainly could be that yours is pretty much done by late evening and you're going without sufficient coverage for a short while. There can be quite a range of activity profiles between different people, so once again, we're all different. For me, Lantus seemed to last around 20 hours. If you brought your evening split back, or pushed your morning split forward, that might solve the problem.
Another possibility is a condition known as gastroparesis, or delayed stomach emptying. This can be a result of elevated blood sugars over a prolonged period. It can cause damage to the nerves controlling muscles in the stomach so that the release of glucose from digestion is delayed. It can equally cause insulin users like us to go hypo as the bolus dose overtakes the digestion process, or cause bg levels to rise significantly much later than expected.
As Sid says, there's also the possibility that the contents of the meal itself can slow the digestion sufficiently to have this effect. Dietary fat is particularly good at slowing things down.
I hope you get to the bottom of it, and let us know how you resolved it. Good luck!
fergus