You can check the heartbeat status of virtual machine via the performance view in the vSphere Web Client:
1. Select VM -> Monitor -> Performance -> Advanced
2. Above the diagramm you can edit the "Chart Options"
3. In the dialog that opens, select "System" and the "Heartbeat" counter
4. You may also adjust the time interval to see if the heartbeat has failed in the last x hours/days
If everything's all right, you should see a straight line.
And if everythin is okay in this performance view, the problem must be in rvtools which is not supported by VMware.
Looks like I'd better put in a call to our support company as it doesn't look like I'm going to get any assistance here...
You get support here if it's an issue with VMware products and not for third-party products. And don't forget that this forum is community driven and lives from the support and work of volunteers. We therefore expect some cooperation from you. However, if you don't want to deal with the problem by yourself, the only way is to open an official support case directly at VMware. That's what the SnS contracts are for. But I can already tell you what they will answer if you report a problem with rvtools. ;-)