Hey, andother z712 question in a row. What are the odds? Anyway, welcome to DCI!
Anyway, looking at the
online version of the manual (pdf) I see a couple of settings that might be worth checking out.
The first is "Picture Size". As far as I cfan tell, this is described on page 28 of the printed copy (page 34 of the pdf version due to its different numbering scheme). From the normal taking pictures mode, press Menu and scroll to "Picture Size". I don't know where that is in the menu as the manual is a bit vague - it sort of suggest that it's the first entry just because of the ordering of that section of the manual, but I have no idea.
The problem is that only seems to give options ranging from the full 7.1 Megapixels down to 1.2MP, which will be something like 1280x960. There doesn't seem to be an option for really titchy 320x240 images, so that probably isn't it.
Next, do you have an SD card in the camera and is it recognised by the camera and selected for use? A lot of cameras that have internal memory impose very strict limitations on its use, such as pitiful image sizes such as this. The internal memory really isn't intended for use by the end user, but is moreso a tool for retailers to be able to show off the camera without having to insert a memory card.
However, the manual is, quite frankly, complete pants. It doesn't mention anything about limitations when there is no memory card present/recognised.
Anyway, where to begin? Assuming you have an SD card in the camera, there are a couple of things that can be checked. The first is in the setup menu, and is called "Image Storage" and is detailed on page 31 (37 in pdf numbering scheme). From the camera's normal operating mode, press menu, then press right on the selector to go to "Setup" (it apparently has an icon that has a camera plus a spanner/wrench) and press OK. From there, scroll to "Image Storage" and press OK (this seems to be the second entry in the list, but who knows?). This should be set to "Auto" to use an SD card - it's the default setting, but it's worth checking.
If that's OK, then iut's probably worth trying to format the memory card (see page 33/pdf page 39). This option is called "format" and seems to be at the bottom of the setup menu. Scroll to it and select, and then from there select "Memory card" and hit OK. If there is a confirmation prompt, follow the prompt to format the card.
If that all checks out and the problem persists, then I have no idea what's going on. The only other thing I can think of is that you've somehow taken a very short 320x240 video, but that's a different file type and it should be really obvious if you're getting movies instead of jpgs out of the camera.