Worth noting that on a reinstall or when installing Blackmagic drivers that your user preferences and most of your prefs in general are reset.
One thing that bugs the hell out of me in FCP7 is the default setting of Realtime audio tracks to 8 and low! Thats the 1999 FCP1 setting!
The amount of old Avid editors that still complain that FCP can't handle many realtime audio tracks is hopefully negligible but I still find myself showing even seasoned FCP editors this!
Put it up to 99 and High!!!
Also stick your playback settings to unlimited when offlining otherwise you'll be rendering basic stuff that most modern Macs cut though like a hot GPU through cling-wrap even on our old 32bit friend.
For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]