This is a bit of a back to the future post. I have recently had to do some work in SSRS 2005 and came across this little issue when using IE9 against SSRS 2005.
If you have report that shows images from and external source inside a cell in a matrix these render correctly in BIDS (I have not tested it with a table but it could be similar). However when you deploy the report to Report Manager you might encounter behavior in which the images are randomly not shown. It does not give a red X showing an error with the image, it just does not render the image.
This can be fixed by placing a rectangle inside the cell in your matrix and then adding the image object into the rectangle. The images are then rendered correctly when the report is viewed from Report Manager in IE9.