Macbook 10.9.5 Firefox freeze
As you probably well know FF had a rough road recently.

Starting with FF 32.0.0 they got up to 32.0.1, 32.0.2 and 32.0.3 in one week while trying to solve a problem that  shows up as heavy CPU loading and sluggish behavior.

They are still working on resolving the issues with last release.

Best you can do is disable all add-on and extensions to test if it gets better.

FYI:

Here is my Console log with FF 32.0.3 Start UP.

kernel[0]: firefox (map: 0xffffff80384f42d0) triggered DYLD shared region unnest for map: 0xffffff80384f42d0, region 0x7fff8cc00000-&gt;0x7fff8ce00000. While not abnormal for debuggers, this increases system memory footprint until the target exits.

kernel[0]: firefox (map: 0xffffff8038d30d20) triggered DYLD shared region unnest for map: 0xffffff8038d30d20, region 0x7fff8cc00000-&gt;0x7fff8ce00000. While not abnormal for debuggers, this increases system memory footprint until the target exits.

firefox[602]: stat on /Users/Buscar/Library/Application Support/Firefox/Profiles/2l6bevrl.default/sessionstore.js: No such file or directory


And the associated Start UP times (from FF Health Report).