Hi @California_Ace - I am getting the same issue too with large PDFs - though for me 50MB appears to be threshold. Did you manage to contact support and get a response?
I was able to get some response from Support on this issue,
Evernote Support are aware and perhaps @Shane D. can provide us updates on when 10.6 will be out - fingers crossed this fixes it permanently.
Having the same issue on Mac [version 10.4.3] to the extent that even the About box goes blank. This seems to happen when Evernote is left open for extended periods of time. I hope this will be fixed soon as its a real pain.