check-out issues (help!)

[DWells]

And then, after it spins for a few minutes, I get this:

CGI Timeout
The specified CGI application exceeded the allowed time for processing. The server has deleted the process.

Sounds like maybe something you should talk to your host about?

If you post your server info-
Host:
Hosting Platform:
PHP Version:
Zen Cart Version:

Maybe one of the other more experienced people on this forum can help you solve these problems.

You might consider compairing the classic template files against your custom template files... the problem of the "add to cart bug" might jump out at you.