This happened to me once. I don't know why or how I resolved it (I know, some help I am). I thought something was wrong until hubby looked at the file size and it was the size of yours and not typical of my file sizes back then. I actually had to re-create the layout. I think it was something on one layer that was the issue. for some reason was way larger than it should have been, larger than it's original. I just chalked it up to me hitting a wrong button. Working with the layout was awful, it took forever to do any function; like, 'save' would take several minutes for the pop up to happen. it has not happened since. To this day I don't know what I did to get the size that big. But I do know a size that big would take a long time to execute any command. Even watching some of the photographers I like using Photoshop, they'll say it will take a minute because the file size is big...and it will only be 50MB, so you can imagine how long it would take for 300 MB or more. Sorry, I could not help since I never found the reason, or what I did to make it happen like that. I think hubby thinks PSP was doing something in the back ground when I clicked save or something else and it added the file size to that layer, I cant quite remember.