Sorry for the very late reply - we seem to have overlooked this. I assume you are updating from a previous Frostwire5 version.
Go to applications and control click on Frostwire > show package dafter ensuring Frostwire is fully contents go to the java folder and find and delete the trident.jar file.
All should now work, although why this should have occurred is a mystery.
Please do not Private Message me with questions that can equally well be posted in the forums, and may also help others. Do use the forum search.