Ready to go live, but helpers won't load! [SOLVED]

[eluser]CoderReborn[/eluser]
After developing my PHP/CI project on my Mac, I'm finally ready to live!
Things have been running great while testing locally.
I installed CI 1.7.2 on a hosted server (running Ubuntu Lucid), uploaded my code, but am getting the following error when I load the site on the Internet.

"An Error Was Encountered
Unable to load the requested file: helpers/my_model_helper.php"

"MY_model_helper.php" is a custom helper in my /system/application/helpers directory.
Curious that the error msg does not capitalize "my".
I don't get this error when running CI 1.7.2 on my Mac.
By setting breakpoints, I found that my program dies in /system/codeigniter/CodeIgniter.php, line 201 ("CI = new $class();")

Thoughts on how to fix this?

Thanks.