I have some news on this problem.
First of all I added the code you suggested and yes, the trigger is always activated.
I have then find 2 different behaviors using Internet Explorer (8) or using Firefox (3.6).
Now, if you want you can test the site at this address:
If you click on the english flag on the top right corner you can see it in english.
In I.E. if you sort wines (for example clicking on "region") and then try to add the first record to the basket, it doesn't work.
But if you then click on "my basket" (it will tell you that the basket is empty) and then click on the back button of your browser, you will find the article in the basket.
With Firefox the add to basket button works fine, but the "toggle sort in subsequent visits" doesn't work....
Any idea? Do I have to attach some files here?