I have an issue with a 404 on my live site, which I think is actually a "Invalid Character in base64 code"

Trying to track this down.. I find that my dev site (exact same as live) has a very small setting hash, whereas when I move to live I end up with a huge hash... anyone able to help.

http://www.kalahari-minerals.com.dev.fidus.co.uk/CuteSoft_Client/CuteEditor/Dialogs/InsertDocument.aspx?settinghash=7feafb84

 

 

ps have to stick with ce5.3 as can't access the code base to amend to new ce6 methods etc... :-(