Dear BlackBerry OS Members,
I always make sure to extensively test every new OS that comes out and report any bugs/glitches since RIM leaves us users in the dark with no changelogs and we have to actually compile that list for them
anyway, I have noticed that OS 188.8.131.520 has a very bad Radio *.sfi file which makes the signal level weaker and sometimes you will not even receive emails or BBM Messages in the right time especially if you are sitting indoors. Which has forced me to downgrade to the next latest OS which is 184.108.40.2063
I offcourse don't EVER do an upgrade or a downgrade before manually wiping my device completely and starting out fresh. It is a big hassle, but I have my very good reasons to do this, one of them being that sometimes in the application management, the list tends to be empty and not display your installed apps, and tha'ts just one of the reasons (too many to list here)
But still, if you are not comfortable with wiping your device manually, you can simply uninstall the 540 OS from your computer, restart your PC, then install 503, delete the vendor file, launch loader.exe, keep watching the apploader folder, you will see vendor.xml recreated again after a few seconds of launching loader.exe for the first time. Delete it again and close/open loader.exe again and select the option to downgrade
Your results and mine may vary and you may not be experiencing the same results that I am experiencing, but many of my pro BlackBerry friends have reported the same thing.
Although this OS is official from Vodafone and recently became official from my Carrier here in Dubai (du) , it is crappy IMO
just my 2 cents