All this works fine in firefox.
In internet explorer 7 and 8, and jquery 1.4.2, the post will fail with a jQuery exception.
The exception occurs when it tries to create an XMLHTTPObject.
Usually if you force a reload of the page, by holding SHIFT+refresh, oddly, the link will then work.
Then go to the address bar, and hit enter so its basically using a cached copy, and the link will fail again.
This is an odd problem, and I dont know how to describe it, but the reload issue is not actually cache related that I can tell. Disabling the browser cache completely produces the same results.
Reverting to jquery 1.2.6 resolves the problem (although there might be later versions which work too)