While opening any jrxml file Jaspersoft Studio Eclipse plugin runs 'Searching Data Adapters' operation. It is consuming much time (it can take several minutes) and resources on large and complex project. Eventually it will find nothing and get error. You can actually work with report - but it consumes those several minutes of hanging - and it can be not one during your workday.
It is related to Jaspersoft Studio Eclipse plugin https://marketplace.eclipse.org/content/jaspersoft-studio (it is rather confusing - you have same name for standalone application and for plugin). I saw some similar reports across internet but they nether were resolved properly. Where are no problems with standalone Studio project, but it is convenient to work with plugin in our project. Where are no issues with older versions of plugin, only with latest 6.5.1 version. Using Java EE Eclipse version.