A lot of the problems (I believe) are related to image size being too large. You need it to be less than 70kb.
I use a free program called irfanview to reduce my image sizes for use on the web. www.irfanview.com Set it to 65% reduction and you should be good to go.
There is a thread that says *** How To Put Big Pictures In Your Post!! ** in the questions and suggestions forum. There still is a link on this board, showing it had been moved.