So, I did not post anything anything for quite a while.
Just to let you all know I fixed the script - it turned out that IE 7 actually uses xmlHttpRequest object, like all other browsers do and I had a variable set inside the xmlHttpRequest object-specific bit, while it should have been in the general bit. Moreover this was a function variable, which made it hard to discover the mistake.
The finished script, which is just a general script to make using the xmlHttpRequest, can be found here. Instructions are found inside the document, this does dramatically increase the size of the document, but if necessary you can cut it out - just the instructions not the notices and such, under the header NOTICE you will find directions what you can and what you can not cut out.
If the need arises to update the script, (there might still be a firefox-bug and there is no support for SEND requests yet) I will update the script at that location and post here that I made the changes. Though it might seem convenient to have your script tag point to it directly, PLEASE DO NOT DO THIS. Download the file and upload it again on your website, this leaves me without bandwidth stains and leaves you with less vulnerabilities (to attacks of mine, hehe).
I made yet another script - a batch script this time. It's a really, really simple script - so if you want to be sure it is nothing malicious, open it with wordpad. If you know something about DOS-commands you will see that it's really innocent (okey, it forces a delete, but that's the whole point of the script).
Okey, I lied, you do not need the file unless you are playing on a private server, private servers change and so your cache might be in the way (if your server crew has never said anything about emptying your cache, this file might not be for you).
Put this file in your WoW folder and run it instead of WoW.exe (or Launcher.exe). This makes sure that your cache is emptied before you start WoW, every time you start WoW. (Of course you might want to change your shortcut to this file and give it back it's icon by clicking on change icon and selecting WoW.exe there).
I hope either of these two scripts can help you, and if not, too bad :P
PS. if you want to link to one (or both) of these files, please link to this post, so I do not falsely identify you as a leecher.