What (operating-)system? What is the Sweet Home 3D version?
An image displaying the problem is always helpfull. Upload the image to an image host like imgur or mediafire and put the download URL in your forum post.

A red x usually means that furniture can't be loaded, most likely because there are not enough system resources available, probably memory.
If you have enough memory in your computer you can increase the amount of memory that Sweet Home 3D is allowed to use. See "How can I adjust the memory used by Sweet Home 3D?" on the FAQ page. Also check that your have enough free diskspace.