Today i run into error

Invalid signature file digest for Manifest main attributes

while running my java web start applet.

I wondered for a while and finally found the reason – yesterday I modified my .pfx key for signing applet, but manifests in jars merge with each other – so I really had jar with invalid digest.

To fix it, I just had to remove META-INF folder from all my jars, add them manifest again and re-sign them.
You can remove it with any archiver – for example, with 7-zip.