I'm using Vue 4.10, and Mover 4. I create an animation in Poser 4 of 60 frames. I save as PZ3 file. I then import the PZ3 file into Vue, and select "Import entire Poser animation". However, once it has loaded, Vue has only sees 2 keyframes, where there whould be 60! On the timeline I press "next keyframe" and it jumps straight to the end of the animation, ignoring what should be in between.It doesn't matter how many keyframes I make in Poser, Vue always refuses to see or recognise them.

Does this sound like a bug, or should I just update? I hate updating because often the patches produce more problems on my machine than they're worth, hence why I'm still using 4.1.

Not sure it is the solution. But try. Could be. So...
Create same frame rate in a vue animation (a blank one) than you poser animation, before importation. For instance if in poser it is 25 frames per seconds, create same at 25 fps in Vue.

I maybe don't understand your question, but I don't think Vue will see any keyframes in your pz3. Only Poser will see them and you have to make your changes there.

Exactly. A Poser animation plays within Vue in a self contained fashion; the only keyframe controls in Vue would be things like if you keyed a texture change. Or shifted the actual Poser file in the Vue worldspace.