Check your poser TEMP folder on the General preferences.

I've noticed that poser doesnt get rid of previously loaded textures even after selecting a new scene, it keeps everything on the TEMP folder (which is C: by default) so after working with a few figures this folder can grow to >10g, if it gets out of space, it comes up with the "No memory" message wich is missleading.

I've seen my TEMP folder grow as big as 30g after opening a few scenes in succesion, it only gets deleted if you close poser.