Can't send encrypted attachments in Outlook 2003

I am having trouble sending attachments in Outlook 2003. Initially I thought it was all attachments, but I have narrowed it down to encrypted attachments. The problem just started all of a sudden. I have had Outlook 2003 installed for over a year, and last week it stopped sending these attachments. I have tried the hotfixes. I have scanned for viruses. I have tried everything except uninstalling and reinstalling. Any ideas???