why am I asked to download stumbleupon application/octet-stream?

Recently I have been getting dialog boxes popping up at seemingly random times asking me what to do with a download from stumbleupon called application/octet-stream. I have not clicked on a download link and I don't know what it is trying to download. I have cancelled every time rather than let the download proceed.

I tried to attach a screen capture showing one of the dialog boxes, but I had already uploaded it on a different forum and now it won't upload here.

I am running Win XP sp3, usually use the Firefox browser (ver 9.0.1) and I am often on Failblog.org when this happens. I recently went through the whole malware removal procedure and my system is clean.

Any idea what this is and what I should do about it?

Thanks,

Dave

 

Tried the suggestion for resetting the firewall and the problem seems to have gone away. Thanks, Plodr.

Dave