What scripts are you using? Infinite Loop detection is based on a watchdog timer. The API sandbox records the time then makes a call into a script's event handler. If some threshold of time passed (I believe it's 30s or a minute...), the Sandbox considers the script to be in an infinite loop. It's likely that a script is doing too much in one of those handlers (they should use a deferral queue or similar), and the congestion on the API server is pushing their execution over that time limit.