You may want to try uninstalling Java and re-installing an older version of it (either 6 or 7). However, this comes with the standard disclaimer that running out of date software (especially Java) may be a security risk.
As others have mentioned, you're running WiNG 4.x software. If you intend on upgrading to WiNG 5.x (HIGHLY recommended) be warned that you will have to redo some of your configuration (you originally had to redo the entire configuration). You have a lot more options available to you with 5.x, such as being able to bridge the traffic locally at your AP instead of having to route it back through the controllers. It does take a mindset change to manage it coming from WiNG 4.x.
Another word of warning though...WiNG 5.x switches from Java to Flash so you're moving from one "evil" to another. I can say with certainty though, that WiNG 5.x works with the latest versions of Flash without issue.
And now my final warning...skip past WiNG 5.2. Things work, but the GUI had some issues. I think the latest version from Extreme is 5.5.x. Extreme had stopped offering new versions as they put the WiNG platform on End of Engineering / End of Support with the Enterasys purchase (WiNG was Motorola based). I can't say what will happen now that they own the WiNG code (through the purchase of Zebra Technologies Wi-Fi business...who had purchased the Motorola Wi-Fi business).
You have to talk to your sales guy to find a way to get this software.
You also have to keep in mind that the AP-3511 is not supported by WiNG 5.x anymore. If you have these APs deployed you either have to update the APs or you have to stay with WiNG 4.x