Drag-n-drop stops working some times

[Mikhail T.]

Most often I have this problem with Firefox, though Thunderbird some times 
starts misbehaving too.

In firefox trying to drag-n-drop a link from one page to an exiting tab does not 
work -- the link does not begin to drag. In Thunderbird dragging an attachment 
from one message to another may demonstrate the same issue.

Restarting the application usually helps, although once or twice I had to 
restart the entire X-session to get the functionality working again.

I can't remember, when I first observed it, but it certainly continues to happen 
with the freshly-built firefox-17.0.1. If it matters, my desktop uses KDE-3.5.10.

Any ideas? Thanks! Yours,

    -mi