Proxy on .mlt not working

Hi there! I am now forced to use an ancient laptop for video editing, and so am using proxies again.

I applied a stabilize to a clip, and instructed kdenlive to make a proxy of the resultant .mlt file.

I get an error message that the .mlt file cannot be loaded, even though it exists in the right place and is readable, as you will see from the screenshot that is attached.

Just on a side note, I am using xfce4 as a desktop to save some resources on this old machine.