If the problem is not listed here, please file an issue at Github.

JPIV stops and throws an out of memory error.
Allow java to use more memory. State java -jar -Xmx4G JPIV.jar to allow 4 Gigabytes, for example.

The Skripts drop down menu does not contain any entries.
Find the jpivlib directory (included in the zip file) and set the path accordingly, as described in the reference.

The vector plots show steps and patches where I expect as smooth vector field.
Check, whether the images show a strong background. This could be a light reflecting structure. Also images with natural seeding (for example using erythrocytes in blood flow) show this effect. Remove the background by a rolling ball algorithm or as described in the HOWTO section. ImageJ is an excellent tool for preprocessing.