Thank you for your assistance, but I've gone over these items for the last few days. I've even re-checked the write permissions on the /files/ folder, restarted the web service, purged the cache on phpBB, purged the cache on the internet browser, and tested in a few other web browsers. Whew! Still, I get the "The extenison *** is not allowed" regardless of what I attempt to attach. Is there something else that I am just not seeing?
I have allowed extenisons for: doc, docx, ppt, pdf, rtf, csv, xls, xlsx, txt (primarily)