before starting, I already submitted this bug to the Calf developers, but I prefer also reproting it here, just in case it could be also related to Ardour 2.
Since an upgrade of GNOME and gtk+2 on the Zenwalk distribution, when I try to set any frequency option on a Calf LADSPA plugin (on Reverb or MultiChorus, for example), I just get an empty grey bar with the default value, and I can’t change it.
I started by removing configuration files from my home directory (~/.ardour2 and ~/.ladspa), but nothing changed. Then I tried with a new user, and I understood it was related to the system.
And I installed Zenwalk on a Virtual Machine, with gtk+2 2.14.7: it worked as before. After upgrading GNOME to 2.26, the same bug occured!
Maybe it’s due to Calf, maybe Ardour 2. Anyway, I thought it could be useful for you to know it.