Sometimes, because of an error in cached data, there are problems with some functions of vesseltracker.com (i.e. log out, create alerts, upload photos)
To solve this problem you have to clear your browser-cache:

• Firefox 2.*
• Internet Explorer 6

• Click on the menu "Tool" -> "Clear Private Data"
  
  
  
• Remove all check marks except for "Cache" and click on "Clear private data now"
  
  
  

• Click on "Tools" -> "Internet Options"
  
  
  
• Switch to the tab "general" and click on the button "Delete files..." in the section "Temporary Internet files
  
  
  
• Press "ok"