I have a simple HTML form, sending a post request to a php script. In IE8, the form only works intermittently - most of the time the PHP script sees an empty $_POST variable
Thanks everyone for wading in on this one.
It turns out the problem lay in an Apache module I had enabled.
It's a module to allow apache to use Windows authentication to identify a user via their Windows User id - mod_auth_sspi
The effect is caused by a known bug, in the module, but with a simple extra directive this can be worked around, until a fix is added in the next update, as described here:
http://sourceforge.net/projects/mod-auth-sspi/forums/forum/550583/topic/3392037