customized checkout, issue with send email

Hello,
I recently customized my checkout on my store. Ever since I did this, every new customer with an order, when i go to send them an email it says: Notice: FAILED to send Email to all recipients: this is when i click send button. I can successfully email customers that I had before I customized the checkout. Any ideas what it can be? What files can I look at that would be causing this issue. Thank you!

Exactly what did you do to "customize" the checkout?

mostly rearranged the layout, and changed headings and color... feel free to take a look, make a fonny name so i know to remove it p e t l a-n-d p l-u-s .com no spaces or hyphens

The mod I used was:
Order Steps - Tableless <Edited the files in there
also, some how my create_account.php was removed so I uploaded the create_account.php from my backup file from 2-14-09

[UPDATE] I have tried the debugger on the admin side and on the includes side, its not finding it. I am able to update the users order status and that does go through. The ty tracker mod also works, emailing the customer the tracking number, its just in the admin ->send email-> select customer-> preview->send mail and admin->customers->click on customer->send mail-> ect both FAIL. What can this be?

What "debugger" in the Admin ?

the debugger mod found in the "free software add-ons"

tried debugger both in admin and includes, remove amazon checkout style and order steps still will not send emails through admin on new orders/customers. BUT for past customer and emails there is no problem...any idea what this can be?