debug cron job fail

I have a PHP program that ran fine as a cron job under PHP4 / linux in a MediaTemple DV 3.0 environment. I migrated the site to a MediaTemple DV3.5 configuration, using Plesk as provided by MediaTemple. The program runs fine (for hours) under PHP5 on the new DV3.5 server, if I invoke it from a browser command. However when the cron job (which just uses WGET) runs, the program fails after a short time. However I can't see any error messages in error_log or the cron log, so I don't know why the cron-scheduled jobs are failing. Perhaps something permission-related was misconfigured during migration? I'm looking for someone who can tell me what's wrong or help me diagnose/fix this.. ## Deliverables 1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No 3rd party components unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the worker's Worker Legal Agreement). ## Platform MediaTemple DV3.5 LAMP stack (PHP5)