uploading via web crashes router on IE and FF but not FTP

>I have 1 gig of memory with Windows XP and the latest updates and I
>use IE7...I have fast DSL. I try to upload a file to Yahoo Mail and
>the attaching of even the smallest file is impossible. The virus scan
>of Mcafee from Yahoo supposedly engages but the upload never finishes.
>However I can use my newsgroup client and FTP and other internet clients but
>as far as surfing anything with the browser...the router is dead. Likewise trying to use firefox for the same sending of email attachments results in the router shutting off all browser connections as with IE.
It is as if my Belkin Pre-N router turns off port 80
>and the Belkin needs a reboot in order to allow me to use it again. The web connection to the Belkin from my laptop works so I call up the Belkin router's web UI and
restart the browser and surfing can resume but no file uploads via the
browser as it would start the cycle again resulting in a reboot of the
Belkin.
Is there a setting that allows or stops me from uploading files via
port 80/HTTP?
Thanks