Latency with only old file

I have never understood where in Preferences the latency settings are for playback and recording. They're confusing. Anyway...
 
I have installed X3e on a new computer and am trying to set everything up the way it was before. I open a brand new file and record midi, and there's no latency at all. But I open a very large file that I built on the old computer, and there's about 0.3 seconds latency on recording. This is true for any instrument or source. On the old computer, which was a much poorer machine, there was almost no latency on recording. 
 
Why has this old project suddenly introduced recording latency, but there is no such latency on a new project?

That is not it. This project (or any project) didn't have this problem on the old computer, using the exact same plug-ins. Some Sonar setting is set back to its default that had been adjusted in the old version.
 
Also, and probably more importantly, this delay occurs no matter what instrument I am using. And only with this project that worked fine on the old computer. New projects do not have this problem.

Figured it out. 
 
Audio > Driver Settings > Mixing Latency
Slide the suffer size to the left ("Fast") as far as it would go without distorting the sound.