I've had a few crashes in the past few days using TG2 2.5 and am pretty sure I know the cause. It's not a big deal and has been a known "characteristic" of the program for quite a while.
I build a lot of my terrains with World Machine and have a habit of naming them ddmmmyyx.ter, such as "18dec12a.ter. When I load a heightfield, I like to change the name of the "Heightfield load 0x" to the World Machine name. The problem is, if the preview window is still rendering when I start to change the name (not the path to the file, just the name) TG2 crashes.
Surprisingly, I seem to be able to attempt to change the name while a regular quick or full render is in progress -- I suspect the changes are "locked out" until the render finishes.
I've trained myself to not make changes during a render -- it only makes sense anyway, but it's so easy to forget the preview is a render and many times you don't realize you've initiated one. Keeping "pause" on the preview enabled seems to work, but then it's easy to forget too.
So I guess the best advice is "no changes when renders, including previews, should be made until those renders finish. Note that there's also the example where you start a final render before the preview finishes and the preview will resume (when the finale render finishes.) It's easy to start making changes to your file, not realizing a render (preview) is still ongoing after the main render has finished.
Maybe the preview should have an automatic mode, like it currently works, and a user start/stop mode, like the regular renders? Then the user can choose.
No big deal, just some thoughts.....