Update: A new FrostWire 4.13.4 installer for windows is now available to help fix this problem, you can just download it again and the problem will be gone. If you don’t want to download it again follow these instructions for a simple fix.
If your new frostwire is crashing, due to :
"Caused by: java.lang.NullPointerException: resource: frostwire_theme.skin doesn't exist."
Just Download and save this file:
http://www.frostwire.com/beta/skins/frostwire_theme.skin
For Windows XP, save it at:
C:\\Documents and Settings\\<name>\\Application Data\\FrostWire\\Themes\\
For Windows Vista, save it at:
C:\\Users\\<name>\\AppData\\Roaming\\FrostWire\\themes\\
(where “<name>” is your user name in windows)
This should solve the problem.
This problem affects only users who never had FrostWire installed on their machine, or users that may have removed their FrostWire Preferences folder.
Thanks to CodeMoose for posting this fix.
Official FrostWire Blog 
when i go to C:\Users\, i dont have the “AppData” folder, why not?
Thank you for this, but a new bug has been introduced. When searching for audio files, I will initiate a search and the cursor will jump back into the “Title” field as files come in.