Hi,
It’s actually a problem with most forums, they can't cope with the picture because it is too big, you can see it fine though because it cache's on you own machine. It’s all computer gobbledygook but basically you have to make the picture smaller before you upload it and then everyone can see it otherwise people will just see a red cross instead. This will probably affect about 80% of the people on here, the only sure-fire fix is for everybody to resize their profile pictures, it will also speed the forums loading time up to for anybody not on broadband.
When you type a posting if you look at the tool bar above your typing there is an insert image icon just below the Italics icon, this is how you add a picture to your posting, however it requires a web address for the picture so you need to upload it to the web somewhere. Free websites like image shack will do this for you or if you have your own website you can use that.
Joe