Download.asp downloads instead of executing

We have been using WebExplorer Pro 2.1 successfully for some time and have been very happy with it.  However, suddenly it's behavior has changed.  When a file is clicked to download, IIS is no longer executing download.asp, instead the web server offers to download download.asp instead.  Any clue what has happened?  I suspect it may be related to SP4 for Win2K, which we recently applied.

Hi Russell,
This problem is related with AspUpload component, please take a look at this thread for more information:
file download

You can try to right click to open a New window.

so you will not download download.asp instead right files.