Your comments

I can't reproduce it. Also, from the comments it seems like it works for other users.
Please provide more information, such as a screenshot, your tweaker's options, and the taskbar properties. Otherwise, I can't do much with your report.
Does the tweaker itself crash, or does explorer crash? Can you provide a crash report?
How do I find event logs when a program crashes?
What do you mean by "it doesn't mess with context menu of Jump List"?
Looks like that's exactly what it does - it provides a way to manage the Jump List.

As far as I know, the HKEY_CLASSES_ROOT items affect the right click menu of files, and have nothing to do with the jump list.
My guess is that you've set Firefox to always show labels.
Please open Taskbar Inspector, right click the Firefox AppId, and check your settings.
I didn't say it has something to do with Firefox.
I said that you have set Firefox in the list of the tweaker to always show labels.
Please open Taskbar Inspector and check it:
http://rammichael.com/wp-content/uploads/2009/09/T..
My guess is that you've set Firefox to always show labels.
Please open Taskbar Inspector, right click the Firefox AppId, and check your settings.
That's not a trivial task. I might get to it one day, but I'm afraid that's not going to happen in the near future.
As for the taskbar width, there's the "no_width_limit" advanced option. Refer to the help file for more details.