This seems to have just started happening. Every file I try fails (HFC:Rejected Local Profile Filter: Filename Filter ...). If I "Add to Download List - Bypass Filters," I have no problems.
I've tried disabling my own filters. Also de-selected "Use Duplicate Detector" in Options. I deleted the Signatures.db3 and let NB created a new one, but that didn't work. I can't locate the source of the problem.
Win 7/64
NB 6.20 Build 1513