This might save someone some time. I created a program to list some rather large files and create links for the end user to click on in order to download them (using the php function fpassthru()).
The problem I was having was it would make it half way through the download (about 377 megs) and the script would terminate and the download would stop.
After doing some shotgun troubleshooting I discovered the php config option 'max_execution_time = 30'. Upon changing it to 'max_execution_time = -1' the files >370 megs can be downloaded without the script aborting.
Jon