What email provider? IMAP or POP mail account? Is the source folder an IMAP folder? Is the destination folder an IMAP folder? Are the folders within the same mail account? What anti virus?

dique said

When I try to move e-mails to a folder the application fails to move the e-mails and I have to restart Thunderbird in order to get the files to move... this is getting so annoying that I am considering abandoning Thunderbird entirely!

The mail accounts are all POP; Thunderbird 31.5.0 (but most earlier versions had the problem, just not to the extent that the current version has... my local folders are shared between four e-mail accounts, but my principal problem is from only one account (the one with high volume reference material to be saved for later use)...

The mail accounts are all POP; Thunderbird 31.5.0 (but most earlier versions had the problem, just not to the extent that the current version has... my local folders are shared between four e-mail accounts, but my principal problem is from only one account (the one with high volume reference material to be saved for later use)...

You did not say what anti virus. It sounds like McAfee, but please I do not guess well usually.