PSP7 - Error Message.

I have checked the memories, so I'm sorry if I have overlooked it somewhere and its been posted twenty million times before.

I've just tried to save an icon in PSP7, it saves fine as a JPEG & PNG but I like to keep a backup psp file incase I may want to update it at a later date and I keep getting "an error has occured while trying to save the image." I've used PSP for over five years now and I never ever had this before now this is the third or fourth time in a matter of days, and usually I just copy and paste the layers over onto a new icon and it saves fine. any idea why it hates this particular icon?

EDIT - Saved as PSD to reopen in photoshop and works fine, still unsolved for the moment as to why it doesn't work in PSP though.