Thomas,
When the version in the client reported is different from the version installed, then probably the client cache is not updated.
There is a version tag missing in the jnlp-file, I have fixed that for next release of the plugin.
As a workaround you can clear the cache on the client.
We are working on getting a new version of the plugin.
We are planning to upgrade to jasper reports 3.7.1, include a number of patches contributed and fixes for issues,
Note that the itext and poi jars in Servoy 5.1.1 have already been upgraded to match the version in jasper reports 3.7.1
Rob