I am running Ubuntu 11.04 with Java 1.6.0_26, and whenever I enter my information in World of Minecraft 2.0.5 and hit "Sign In" I keep getting a fatal error with java.util.ConcurrentModificationException and if I run World of Minecraft.sh through the terminal, I get the same thing and in the terminal it says:
Constructor for World of Minecraft : java.net.URLClassLoader@41d5550d<br>Couldn't load connection cache: java.io.FileNotFoundException: /tmp/World of Minecraft-cache.dat (No such file or directory)<br>java.util.ConcurrentModificationException<br>    at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)<br>    at java.util.LinkedList$ListItr.next(LinkedList.java:696)<br>    at com.World of Minecraft.CookieList.get(CookieList.java:33)<br>    at sun.net.www.protocol.http.HttpURLConnection.setCookieHeader(HttpURLConnection.java:1079)<br>    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1376)<br>    at com.World of Minecraft.ServerDialog.fetchUrl(ServerDialog.java:608)<br>    at com.World of Minecraft.ServerDialog.validateLogin(ServerDialog.java:679)<br>    at com.World of Minecraft.ServerDialog.<init>(ServerDialog.java:107)<br>    at com.World of Minecraft.Wom.run(World of Minecraft.java:264)<br>    at com.World of Minecraft.Boot.main(Boot.java:160)

I'm not a Java expert, so I'm not sure if this is a Java or a World of Minecraft problem. The help is appreciated.