Here is the BEST way to install this OS and to overcome the hidden BBM Cursor Bug.
Note: The following guide is not recommended for novice users who are not yet comfortable installing / modifying files on a BlackBerry. If you choose to follow the guide, you take the risk should anything go wrong.
1) Download OS 188.8.131.521
2) Install the OS on your PC (it is recommended that you uninstall any previous OS you had installed before although not mandatory)
3) Backup your BlackBerry settings/emails/contacts using the BlackBerry Desktop Manager
4) Navigate to Computer >>> C: >>> Program Files (x86) >>> Common Files >>> Research in Motion >>> Apploader
5) Delete the Vendor.xml file
6) Download and extract the files of BBM 184.108.40.206 from HERE
7) Copy all the COD files in the folder you just extracted to the following folder and overwrite all the files when prompted to:
C:\Program Files (x86)\Common Files\Research In Motion\Shared\Loader Files\XXXX(your 461 OS FOLDER\Java
8) Shrink your OS using BB Boss or Shrink-A-OS (optional step and not neccessary to complete this guide)
9) Run Loader.exe to start the installation of your new OS.
10) After the OS has been loaded and the device restarts, launch BlackBerry Desktop Manager, then click Restore from the top right menu, then select the backup file which you created in the 3rd step.
You now have the latest leak and a working BBM with the cursor
By the way guys, I did not include the instruction to backup your apps via BBSAK as that will also backup the current BBM which will get us back to square zero, and thus it will not work.
Also, do not attempt to manually install the new BBM files to your BB via BBSAK thinking you will ssve yourself some time by not reinstalling all the OS and all your apps again, as BBM will not run and it will ask you for a keycode
Unfortunately, the only way to have this cursor show is to do it the heard way by manually installing all your apps later.