Sounds like it may be too big. If you are running Windows, right click on the picture file and go to edit. It should open up in Paint. If you go up to the top right of the window, you will see a resize option. Click that and it will bring up a window. Click the pixels option and type in 150 into the horizontal field. The vertical field should auto resize based on your horizontal input. Hit ok at the bottom and then save the file. You should be able to upload it without any issues after that.
I like your user name, low-tech being my situation as well. I finally posted my avatar but left it sideways for want of remedy -- the photo started out right-side up on my screen -- until some technically adept person turned me right-side up at at last. Welcome aboard! Hope to see your avatar soon. I'm afraid I'm sort of a parchment and quill pen person myself.