The correct site for uploading is ftp://ftp.avast.com/incoming/, and it is write-only, which means that you can’t see the file after uploading it.

Please use a zip archive before uploading it, and name the zip archive with a unique name (like for example Mac_the_Knife2011NOV08-1.zip.

You may want to include in the zip also a text file with more info and the link this this topic (very recommended).

May I ask, do you have SP3 installed?