Slapnpop,
You are experencing a buffer overrun, which is caused by the PC sending too fast.
You can fix this by adding line delays or at worst, character delay.
If you need more help, give me a call and happy to give you some phone time.
Predator DNC will do it with no issues loading, receiving or drip feeding.
I can even give you a great reference of some who struggled for months with all the favors of DNC you mentioned and finally came around to Predator with a live support person, not just emails behind some $50 DNC package of the web.
Greg Mercurio -Shop Floor Automations
www.shopfloorautomations.com /619-461-4000