image upload 0 pixels

Dear support,

I integrated FCKEditor on my website, and everything is working perfectly. Except: when I upload an image through the default image uploader, the following occurs:

1. I select 'upload image'
2. I choose 'browse on server' (bladeren op server in dutch)
3. I select a file and choose 'upload'
4. I select my uploaded file and get to the prior Image Popup Window
5. Here the dimensions of my image are 0 x 0 pixels!
6. I reselect 'browse on server'
7. I reselect my uploaded file
8. Now the dimensions are OK

I figured out this 'work around', but my clients aren't. What is going wrong here?