Elyse,
I used the Mabry control (the FTP one, not the mail control) with VFP a long time ago. I believe I was able to use Debug with their FTP control.
It could be the AutoYield setting, it could be a couple of things. The Mabry FAQ site was always very good about documenting issues with VFP. If you go to
http://www.mabry.com/faq/index.htm and search the page for FoxPro (you'll probably find several hits), you might get some information.
Kevin