Oh, I thought you had been talking about menu icon when discussing this on irc.

Screenshot?  (would help).

Otherwise, can't imagine this being ktorrent's fault.

Can't reproduce.

1.  Applications->Internet->ktorrent
2.  ktorrent systray icon appears

I can't verify this here.

Please check the following things:
- Which version of ktorrent are you using? (Help, info)
- Do you actually see the ktorrent symbol in the Gnome menu?
- Does the problem also come up if you create a new user and launch ktorrent 
there?
- Is there any error output when you run ktorrent from within a terminal?

okay, I moved my ~/.kde dir to ~/.kde.bak and this fixes the problem.  I must
have set some alternate icon set in KDE which caused this.  Using the default
icon set fixes the problem for me.

Ok, I mark this bug as fixed since it looks like it is not a ktorrent bug at 
all, but rather an icon set problem or a KDE problem in general.

Please reopen the bug against the right KDE component. Try to narrow it down 
prior to filling the new bug to make sure what exactly causes the bug. For 
example you could
- change the icon set to check if that is the problem
- copy back the parts of ~/.kde.bak application for application and check when 
the bug hits in

Also, the description of the bug is still not clear - you haven't answer the 
question if the icon is missing in the system tray alone or in the Gnome menu 
as well.

If it turns out the bug indeed depends on ktorrent, please reopen this bug 
report.

On Linux Mint / Cinnamon, I fixed this issue using:

rm ~/.kde/cache-$(hostname)/icon-cache.kcache