When does the message pop-up, before or after finishing the render?
Do you use a network render?

I had a similar problem in 6.5 rendering with HyperVue. In the end HyperVue crashed wile compiling the picture. I think it hit the limit of my system memory or the amount of memory Vue can use.

Oh, by the way, I'm testing Vue7.5 right now and there is a bug that does not allow me to write to anywhere else than the default pictures/e-on software/ Vue... etc. I would not be surprised if the same bug exist in 7.4 If so, you also need enough space on that disk...;-(

Good luck