"The specified release was not found."
I removed it, the plugin-container was malfunctioning. Just rebuilding it now, should be ready in a few hours :)
So the rebuild hasn't fixed the issue, it seems that Adobe Flash is the only plugin that causes the crash! This is annoying as it sets back the build.
Found the bug: https://bugzilla.mozilla.org/show_bug.cgi?id=899026
Turns out it is fixed in Firefox 26.