I have a test save with just myself playing hyborem, deleted the AIs, and surrounded myself with burning sands. No patch and it crashes first turn every time I load it, and usually first turn if I remake the test (sometimes I get one or two flames to show up, it always crashes pretty quickly though). First patch doesn't do anything, crashes the same way. Second patch seems to stop it crashing completely (fixes the save I uploaded too). Third patch crashes same as no patch. Fourth patch was unusual, it made the save I posted in the bug thread not crash the first turn, though it crashed like 4 turns later anyway. The other test save crashed instantly as usual.
I tried to make a few big forests and set them on fire with imps blazing, first time it crashed the first turn, but I tried again and got a nice blaze going, no crashes. Maybe I messed up the test first time, kinda tired

Would be surprising if it was flames per se though, I should've noticed that, even though I don't use blaze/Acheron much. Plus they do work, just not always.
Anyway, must sleep now, hope that helps!