BUG: Iceweasel opens new window instead of tab (external links)

[Frederik Stadtmann]

Hey everybody
after the last update to Iceweasel 20.0 external links (Icedove,
RSS-Reader etc.) are opened in a new window instead of opening in  a Tab
in the existing window.


Changes in about:config show no effect, current config:

browser.link.open_newwindow 3:
browser.link.open_newwindow.override.external: 3
browser.link.open_newwindow.restriction: 0
browser.link.open_newwindow.restriction.override: 0

Tried disabling all Adons (Safemode): No effects


OS:
Sqeeze


Fred