Http Request send occassional fail Firefox

I create a http.request and set up a couple of parameters then GET from the same host as the calling page. This all works fine - everytime in IE8 - but sometimes fails in Firefox 3.5.8 with an error:

uncaught exception: [Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIXMLHttpRequest.send]" nsresult: "0x80004005 (NS_ERROR_FAILURE)" location: "JS frame :: http://127.0.0.1:8501/aw255runtime/source/lib/http/request.js :: anonymous :: line 200" data: no]

Anyone got any ideas why the request.send should sometimes fail in FF?

Found some info by googling for:
0x80004005 (NS_ERROR_FAILURE) [nsIXMLHttpRequest.send]

I should have said that the problem wasn't covered by the resources I had found through Google - always my first step to solving a problem.

In the end I tracked it down to the maximum size of a HTTP header. I am using headers to send back data from a database. If the data being returned in a single header grew beyond ~10,000 bytes firefox just gives up and you get nothing in firebug to say what happened.

Partitioning large blobs of data into a number of smaller packets, each in its own header, solved the problem.

If anyone knows what the maximum header size FF3 can manage that would be helpful. I couldn't find that through Google so the byte limit I used was found by trial and error.

Chris,
Have you tried changing any/some of Mozilla preferences ?
about:config
network.http.request.max-start-delay
network.http.request.max-????

Just a thought
HTH

Carlos

I haven't, but since it would be a headache to ensure all the users of the app had their browser set up a certain way, I wouldn't want to go down that route unless I had too. Thanks for the thought, though.