.....I'll bet you a million bucks, the image you are trying to upload is too big. The attachment tool on stangnet will only take a picture with the max size of 78.1K. The size of your image will vary depending on the setup on your digital camera. I'd say most of your pictures are around 500K. You need to resize your photo before you can upload it....
....another alternative is to find another place to host the pictures. I was turned onto photobucket.com by a fellow friend on another board. It's free and can hold up to 1 GB worth of pictures. You can pay for more space, but I found that is enough for the purpose that we would use it for. Good luck!