When POser tells you that you have a memory problem it means that you have not a memory problem,  but you have a Poser's problem.
Textures comsume a lot of memory, but today you have a lot of memory too!
A texture of 4000x4000 will use 48M, if you use 40 of then you have only used 2GB of memory and today's computer have several GBs of RAM and don't forget that virtual menory (disk) extends the total available memory and who decides to use RAM or disk is Windows and not Poser, Poser only request memory and Windows allocate it.
When you run of memory physical + virtual your Windows crash or becomes very very slow, windows and dialogs of any application lose colours and so on, better restart your computer if still it respond.
Poser can give you messages that has no memory even you render only the background plane at 600x600.
One reason I found was a corrupted Poser.rsr, if I overwrite this file from a backup copy Poser returns to work normally.
Other reasons can be corrupted pz3, cr2, pp2 files, you can correct them with a text editor if you are able to find where the problem is, if not you must start all again from ground zero and the files are lost.
A buggy geometry can be the guilty, this time it was not a Poser's guilt, only he got crazy with wrong data.
On the other side I was able to render complex scenes with only 160M RAM and 100M virtual memory.
Even today I have only 500M RAM and my virtual memory is limited to 700M (I can extend it if I wish, disk space I have a lot) and I use a lot of textures and many figures, the only penalty if I overload the scene is that it takes a lot to render, of course with more RAM it will render much faster.

Stupidity also evolves!