If you can find it, SnapVMX script was always helpful to me to straighten out snapshot chain issues. VMWare support hooked me up with that one and it was used by them on our issues that kept reoccuring due to some less than stellar backup software.
Also worth mentioning - some of my fellow engineers relied a little too much on snapshots, making my datastores a complete mess. I ended up retrofitting a PowerCLI script to go through vcenter and identify which VMs had snapshots older than a couple of days. That script would be run via a scheduled task every day and email me a report...so I could yell at said engineers who had stuff kickin' around. It might be worth spending the hour or so getting that going.