When reviewing the logs for the Snapshot and errors download the logs then go to the Task directory and critical_error logs to see if you have errors that are not presenting themselves. Could you also send your logs to support@open-e to have our engineers review them to see if there is an issue.
Also I wanted to update you that if you are using the 64 bit kernel there is a current bug, so we have blocked this when running more than one Snapshot until new fix has been completed.
If you went into the Console screen then ctrl. + alt. + t (Console tools) then selected Boot Options > System Architecture > Single or Multi proc. 64bit. But it does not sound like you went this deep into it. Send logs to support and ask them to check this issue with the Snapshot when using 2 on separate times on same volume. Could be something else is going on.