problem with revert to snapshot function

Hi

I am having problems with the automation of VM ware workstation 6 with multiple snapshots. On revert to snapshot sometimes it tries reverting to the wrong set of files and I get a vmdk problem. ( file missing )

1. Have you seen and over come this?

or

2. Have another way to automate VMware where this does not happen?

Host is on Win 2003 and XP. Guests are XP. We are using VIXAPI to do actions like : poweron, poweroff, reverttosnapshot etc.

Regards

Minu