Hadn't used my phone to post pics for a while, so I got the "file too big" message last night.
The message I got is maximum size is 800x640.
I found a free Android app called "Image Shrink" that allows you to set your desired image size in pixels. Really easy to use. Go to your photo gallery, select the pic you want to upload and touch your "share" button. You will be prompted with several icons for where you want to send your image; one of those will be for the "Image Shrink" app. Touch it and done. The app will create a new photo album on your phone for the smaller image, which you can upload normally.
Hope this explanation is clear as mud......