Sorry playing catch up here
What os do you have installed on your phone now? If it is a straight OS then do the following
Delete OS off PC through control panel add/remove
then navigate to C-programs files-common files-research in motion-shared-loader files- and delete anything in that folder.
Now on your phone delete any bbm that may be installed
Empty recycle bin then reload the OS you have installed on your phone back onto pc. Then run loader.exe and and it should update your core apps and put bbm back on the list to load.