1. Could you provide us a list with the plugins that are causing crashes when they are scanned (or used)? Often these sorts of problems are very easy to fix, but we need to know the plugins that are causing them before we can.
2. Could you describe exactly what you did before the crash occurred on your 44.1 file (i.e. opened the file, made x and y edits, applied effect z, then undid and *boom*)?
Also, a reminder: if you haven't already, always submit a crash report in the Adobe crash reporter when you crash, with basic information. We track these pretty closely, and they can be extremely helpful in tracking down issues.
For the crash on the built-in plug-in... if you delete the following file from your application preferences, does the problem go away?