In some cases, a template is unexpected closed due to system crash or power failure. So when another user try to open or update the template, he/she will see a warning message like: 'Template is being used'. It can be solved only by the users who have the 'Administrator' authority:
1. Open "Management Console"
2. Click "Excel Report", and select the unexpected closed report template;
3. Right click it and choose "Properties";
4. Click "General Information" -> "Close Report".
After above steps, the report template could be used normally.