No longer works after Firefox updated to 12.0

[GoogleCodeExporter]

What steps will reproduce the problem?
1.Update Firefox to 12.0

What is the expected output?
caption titlebar is hidden

What do you see instead?
the caption titlebar

What version of "Hide Caption Titlebar Plus" addon are you using?
2.6.0
What version of Firefox?
12.0
On what operating system?
Windows 7 Ultimate

- Please provide any additional information below.

- Please provide your system info by using this url (with installed hct+):
  Name of the browser (appName) Netscape
Name of the browser vendor (vendor) 
Code name of the browser (appCodeName)  Mozilla
Engine of the browser (product) Gecko
Build number of the browser engine (productSub) 20100101
Version and platform of the browser (appVersion)    5.0 (Windows)
Version of the browser given by the vendor (vendorSub)  
Build identifier of the browser (buildID)   20120420145725
User-agent request header (userAgent)   Mozilla/5.0 (Windows NT 6.1; rv:12.0) 
Gecko/20100101 Firefox/12.0
Language of the browser (chrome-locale) en-GB
Language preference in the browser (useragent-locale)   en-GB
Cookies are enabled (cookieEnabled) true
Operating system (platform) Win32
Information about the OS and CPU (oscpu)    Windows NT 6.1
System is online (onLine)   true

- If there are visual issues, please provide also screenshot/s (preferred
uploaded here instead of external link)

Original issue reported on code.google.com by philip.a...@gmail.com on 3 May 2012 at 3:43

[GoogleCodeExporter]

I've just realised that this must be the same issue as 178, 183 and possibly 
192 except that I'm on the Firefox release update channel. Apologies for the 
double post if this is the case.

Original comment by philip.a...@gmail.com on 3 May 2012 at 8:20