IE can be very stubborn. I've had issues with it caching cookies it shouldn't have, and to my dismay there wasn't much I could do to beat it into behaving. Adding a Cache-control header as dws proposed is avisable - in fact, I advise sending actual headers rather than the META tags you have.

On the other hand, in your case it sounds like it could well be an issue on the server side, as though your script is being kept alive after one invocation and won't accept data after one run; after some idle time it's killed, and then takes data once more when it's rerun.

The fact that behaviour differs depending on user agent is odd however - either way.

Maybe it's due to some strange kind of HTTP/1.1 keepalive handling? What configuration are the scripts running under? What exact browser versions have you tested this with? Specifically IE's behaviour can change from one build to the next - obscure bugs crop up and disappear overnight. Really frustrating.

Makeshifts last the longest.