I have a curious problem at work which I've been struggling with since the advent of Windows Vista.

We send our own email newsletter out to 40,000+ people once a week. The sending code has been in place for years, it's in classic ASP/VBscript called through a browser and simply loops through each email address, sending it to them. The page takes 40 mins or more to run, so has a big timeout value to allow it to do so.

All well and good, suddenly, after Windows Vista is installed on the work PCs, the email sending page behaved oddly - after a period of time it seems to reload the page, endlessly, so the first 20% of our users get multiple copies of the newsletter until we kill the process!

If we run the code on an XP machine in the on the same office network, it works fine. If we run it on Vista outside the office, so, say, on my own ISP, then it also works fine!

Note, same effect in IE and FF...

So, something about my office network and Vista is causing this...

I recently re-wrote the newsletter code so it would split the task into chunks of 100 users at a time, hoping this would fix it, but my most recent test shows that the office n/w vista machine once again reloads the same page over any over, even though it takes 1/10th of the time to run...

Does anyone have any ideas what it might be, how I can prove it, or, better, how I can get round it?

Thanks for your advice :)