Problem Player Can't Log onto FTB Unleashed Server.

[GBattaglia]

No other players are reporting this issue, but one player cannot seem to log on. I can't seem to figure out the issue and I'd great appreciate any help regarding this. So here is what it shows for him:

[19:20:39] [ERROR] ClassLoader.checkCerts:-1->MinecraftLauncher.main:217: Unhandled error launching minecraft: java.lang.SecurityException: class "sq"'s signer information does not match signer information of other classes in the same package

2013-08-01 17:01:19 [INFO] [STDERR] java.lang.NullPointerException
2013-08-01 17:01:19 [INFO] [STDERR] at net.minecraft.client.gui.RunnableTitleScreen.run(RunnableTitleScreen.java:33)
2013-08-01 17:01:19 [INFO] [STDERR] at java.lang.Thread.run(Unknown Source)

Any ideas?

 

[Lawbroken]

Update Java

Backup launcher folder and ftblauncher (found in roaming) search %appdata%

Then delete and reinstall a fresh FTB launcher.

If this doesn't work we will need a full log and not parts.

Edit : Also found this on my rounds of the forums.
http://forum.feed-the-beast.com/threads/really-urgent-someone-plz-help-me.27212/page-2
same problem.