Minecraft has migrated all their data to a new server cluster. Womclient seems to be struggling with the change.

What is happening is womclient is getting updated, but the file
"minecraft.jar" isn't on the server it used to be, so the minecraft.jar
in your womclient/lib folder has become 0kb. Empty. You need to
re-download minecraft.jar from :

https://s3.amazonaws.com/MinecraftDownload/classic/minecraft.jar

and put it in your womclient/lib folder. Keep a copy of womclient and
the minecraft.jar file because might have to do this again later.

To prevent womclient from updating again do this :

1. Disconnect from your network.
2. Start womclient , don't login yet.
3. Re-connect to your network
4. Wait a few secs to be sure you are connected properly
5. Login to womclient.
6. Pray you can connect to a server.

Sometimes you have to repeat this sequence several times before you have sucess. Don't give up after one try!

This is the only semi-reliable solution at the moment.