How do I stop - "Application/json" file down load popup?

First off, I'm not sure this is the correct forum, secondly I know it's not strictly a W7 problem, but, I'm now so desperate I'll try anything.

In Firefox the home page is set to Google search by default. When I type in a search it works as expected. If however I try to modify the search in the same window a popup comes up saying "Application/json" is ready to dowload a file, where do I want to save it? In fact multiple popups open (could be upto 10)

It doesn'e matter if you choose to download or not, nothing happens. It just keeps repeating the loop.

Does anybody know what is going on and how to stop it?

I'm getting no response from either Google or Firfox on this issue.

No, 10.0.2 which "should" be the latest version, however, it has been going on for at least 3 months now, which I know of, that means at least 5 - 6 updates have come through non of which corrected it.
It just seems strange to me there is very little on the net about it. Surely I can't be the only one who is experiencing it.
Google and Firefox have never responded despite many emails and feedback requests.

I've also taken out all plugins.

What do you mean by, "if I try to modify the search"?

The very first thing I type in the search box works as expected. eg - "Windows 7". A number of search results will come up. If I then go back to the search box and 'modify' the criteria. eg - "Windows 7 problems", before I can even type in the first letter of the modified word "p", between 1 - 8 boxes open up asking where I want to down load the file - "Application/json". I could provide screen shot but I'm not sure that would be of help. It is the fact that the search is diverted to the appl/json dialogue box instead of providing the search results.

Once it has started to do this it is imposible to use that search box again. You have to close Firefox and reopen.

Funny thing is, it doesn't happen with the Google search box located in the tool bar at the top of Firefox home screen, that works as normal.

I see what you're saying now and that is rather weird. So you've disabled or removed all plug-in's so there are none resident at all within Firefox, correct? How about your extensions? I would disable and/or remove all of them as well and see if the problem persists. If it is fixed, slowly add them back in (making sure to install the latest versions for each) to see if you can narrow it down. I searched a bit on this issue and it seems to be tied to an interfering extension.

Sorry, I meant extensions. I don't have any plugins at all. I know what you mean about some causing problems, certainly one called FastestFox has been implicated, but, I eliminated that from the equation and it still happens.

What is also peculiar is when I try changing the search text even by only one letter, at least 3 or 4 popups come up asking to down load the file, so, the problem doeasn't seem to be related to the number of charactors changed/added to the search pane.

For completeness I'll try to upload a screen shot of the messaage box

There are 3 boxes open in the above screen shot (stacked) even though I only changed the last letter