What the -image does is re-download your gw.dat file. This file on your computer contains most of the static information in the game. It is a very long download so best done while away from home for several hours or overnight.
1. rename your current gw.dat file
2. follow the instructions for converting your Guild Wars desktop shortcut to add the -image command
http://wiki.guildwars.com/wiki/-image#-image
3. Double click the converted Guild Wars shortcut
4. go to bed or school or work, etc.
5. When the download is complete, remove the -image from the shortcut
6. Start the game and hopefully your problem will have disappeared.