I am getting the "gallery not found" message as well.  I am using dreamweaver.  I upload all simpleviewer files to my directory via ftp.  Then in dreamweaver I put the cursor where I want to insert the movie and I go to "insert"  then i choose "media" and then "flash" then I save the file and when i go to view the webpage it says "gallery not found".  The "index.html" file works fine on my computer but not after I upload it. 

my file structure is upptampabay with the www before and dot com after and then simpleviewer slash viewer.swf

but check out www upptampabay dot com slash test dot html

so that works....why doesn't it when I insert it into dreamweaver?

What more information can i give for you to help me out?  Thanks!