Uploading a file/image here is not exactly intuitive. It is really a three step process.
1. Put the cursor in your message to tell the software where to place the image/file. Otherwise, it will end up at the end of your message.
2. Choose an image/file to upload. Looks like you probably did that part.
3. Click the "Upload" button.
4. Wait for the upload to complete.
5. Click the "Manage Current Attachments..." There should be a number showing how many images/files have been accepted/uploaded. Of course, the title is just a
little misleading, since nothing is really
attached, yet.
6. Click the tiny disclosure triangle to see the list of images/file you may have uploaded.
7. This is the tricky part: Click the file you want to actually attach.
There, that's at least three steps.
I suspect that you had only one image and even clicked the disclosure triangle but failed to actually select the only possible file available (stupid software!). Thus, the software assumed you are an idiot and gave you the oh so helpful error message. Since it already has the list of
one file to attach, why not just attach it instead of bothering with an error message?
Actually, the software, with just a bit of programming, could simply upload each file in sequence when asked or just the file you select, incase you want one more than once or some not at all. But, that would require thought about how the user would do things instead of how the programmer thinks it should be done. Besides, humans are so unreliable, confusing and demanding...
If the above is not what happened, maybe you really are in need of re-training! I know it helped me and only took 12 years!