After waiting 12 hours for a render to finish last night and saving the .bmp, it refused to open.
Something about "corrupt file". Damn!!!!
Not only would it not open, I couldn't even send it to the recycle bin or delete it from my desktop.
On starting my PC this morning the file has disappeared altogether.
I don't normally have the patience to wait that long for a render but it did look very nice with ambient occlusion lighting.
It might make me feel a bit better if others shared similar experiences. Twelve hours is huge for me but I'm sure others have worse tales to tell. Bring them on.