Have you cleared both compiled-code caches, i.e.
1. The one in <National Instruments>\LabVIEW XXXX\VIObjCache\(...)
2. The one in <Documents>\LabVIEW Data\VIObjCache
I think the recovery files are also somewhere in LabVIEW Data folder... Maybe just try to wipe this whole folder?
Also: the crashes at the startup happens when LV have problems with loading project providers. Any toolkit you've installed recently? Or just go to the <LabVIEW>\resource\Framework\Providers\GProviders folder and remove it's contents to see if LV will start without them, this will narrow down the problem.